Dedicated Servers ----- So to start out, a dedicated server for games just means that the server is one thats running on the official game server files that can be downloaded from Valve freely, which is made just to run a game server alone, so there is no actual game screen you see, its just a version of the game you start but runs in the background, instead of having its own window, and its set up slightly different to make a game server available to be connected to on that server PC by players.

(in this case the Server PC running the Dedicated Game Server runs and controls the zeds, special infected, and other world elements etc. so the players PCs just send info about what the players char is doing or where it is when it moves or shoots, compared to a single player game where the players PC handles the whole game world, and their own players movements and actions)

Technically Dedicated Game Servers dont have to be, but are usually run on a Dedicated Server PC somewhere, which are the same as other PC's (for the most part) but has a server operating system installed, (like windows server 2012 or a form of linux etc.) so its meant to run just game servers, or website database servers so when someone searches for that said website, the closest dedicated server to them for that website will send the info for the websites page back to them, allowing their PC to load the web page, or whatever other internet based service.

Thats what a Dedicated Server PC is or also known as a Server Box, and the Dedicated Game Server version of the game is the official Valve (or whatever the games developers) download for the game server version of a game to be run, which can support 1 match at a time per instance of the installed game server.
So theres kinda 2 meanings to "Dedicated Server" depending how your looking at it, a Dedicated Game Server Installation or the Dedicated Server PC that the game servers are run from.
  
  
  
 
 
 
Non-Dedicated Servers ----- are servers / matchs that are run off someones PC that comes from the same game files everyone uses to actually play the game, so if you pick Local Host when starting a match thats what a Non-Dedicated Server is (also known as a listen server) which is basically like if your PC was running a single player match but it just let ppl connect to your game / PC, which is why the ping / latency is usually so bad for everyone but the hosting player, cuz the average internet connection cant match a dedicated server hosting companies net speeds, and since the Hosts PC is the 1 running the match / games world / zeds, they have 0 lag time.

So if you host a Local Host match be sure your using an Ethernet Cord and not Wi-Fi, it doesnt usually make much difference when your joining a Dedicated Server using Wi-Fi, but for the other players joining a Local match run from a residential internet connection, it makes all the difference for the Host to be using a hard wired Ethernet cord connection, instead of Wi-Fi. (trust me your friends and/or current teammates will thank you lol)
   
   

("options under Server Type lobby setting")
 
 
 
 
 
Local Host ----- this means the Lobby Leaders / Hosts PC runs basically a single player mode and allows players to connect directly to their PC, which is why the lobby leaders ping is usually 5 or less and everyone elses is normal or really high, but this usually has a few performance issues or incompatibility when the host is using mods that the others dont have, so these are Non-Dedicated servers.



Steam Group Servers ----- the steam group servers are servers hosted by clans and steam groups (sometimes by individual people) but they are usually still Dedicated Servers, and of course since these servers are privately owned even if they are publicly usable, the groups usually mod them to change the gameplay to what their players like.
(some groups do run default 4 player L4D2 servers as well so they can install Workshop / Custom Campaigns / Maps to them and play, since the Official Dedicated servers cant run any custom campaigns and you have to end up using a Steam Group Server, although those are usually set to private so you have to join their group before it lets them show up for you, that way the groups default servers are not always full so the groups members can get in to play, or start a match to the server from the lobby without it being full majority of the time)

When you start a lobby / match with the Server Type setting set to this Steam Group option, it gives the lobby leader a list of the public community servers to pick from so you can choose what you want to play, just dont let the players in the lobby vote to start or when the count down ends it will pick one randomly.



Official Dedicated ----- these are servers that are run by Valve which is all official means, they are the same exact thing as a dedicated steam group server that just isnt modded at all, that is if Valves and the Group server PCs have the same power / performance. (just to be clear cuz i see people think they're much different really often) These servers cant run custom campaigns from the workshop or other file hosting websites.



Best Available Dedicated ----- when you choose this option it just means that the lobby will check for the closest open official dedicated server, if it cant find one then it starts looking for the closest open steam group server that is a dedicated server, and if it cant find one it tries to do Local Host on the lobby leaders PC.
So if you set Best Available Dedicated when going to start a lobby thats playing a Custom Campaign, then you may as well set the Server Type to Steam Group Server instead since thats where you end up anyway usually, and that way you can pick the server you want to play so it doesnt stick you to a random one thats got some crazy mods or something you didnt want. (unless the crazy mods is what your looking for lol i dont judge)

(but again, just dont let the match start by the players voting to start, cuz after the count down it will pick a random steam group server instead of allowing the lobby leader to pick one)

If you currently dont know of any Steam Group Servers that have the workshop / custom campaign installed you want to play, then just auto start the lobby with this Best Available option for the Server Type setting, then let the game connect your match to a random Steam Group Server that has the Map / Campaign installed.
Then when you find servers you like the settings, check the MOTD page for a link to their group or however they set it up for players to find their servers for use, although sometimes the MOTD's built-in link to the steam group doesnt like to load next to the OK button that dismisses the MOTD page, so open it a couple times if it doesnt want to load at first.
(open the Dev Console in L4D2 with the ~ key and enter the command openserverbrowser to see the old browser for adding Favorites or checking the History tab for a recent server you used, which is really helpful for the servers with no steam group connected to it)[/i]



Ping ----- Figured i should put a tip in for ping as well (also known as latency), so ping is a representation of the time it takes for your connection and the game server's connection to communicate, so if you start a local host match and your friends are far away then they will have a high ping number, high ping number means the player will lag and react at a later timing.

*The way ping works is its a hundredths of a second decimal value, so if you have 100 ping then it takes 1.00 second for your actions to reach the server, or if your ping is 658 then it takes 6.58 seconds for your actions to be recieved. So you usually want it below 60 but the lower the better, if your ping spikes up high then back down randomly its probably your internet connection but if you have a steady constant high ping then it usually means your far away from the servers location, or someone else is using the internet connection at the same time as you on another PC or Xbox etc. cuz that can make you have lag spikes or even constantly high ping depending on what the other person is doing on your internet connection at the time your playing.
 
 
 
 
 
 
*Side note, if your steam profile view setting is set to Private or Friends-Only then you wont see any of the Public steam group servers you can start a match on unless you join its steam group, so if you see 0 steam group servers on the main menu of L4D2 that is probably why

There is actually some 300-400 servers to use in there if your profile is set to public, or if you join a steam group that runs servers then their servers will show up for you in game so you can use them.

(EDIT: not sure if this is still the case after the Last Stand update, it may have been altered cuz it acts kinda funky now, or maybe it was partially broken when Steam updated the user profile settings)

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You can also check the Steam Page here ---> https://steamproxy.com/app/550/discussions/1/

which is a community groups / servers sub discussion forum i guess in the L4D2 steam community hub

although not a lot of ppl post there with info about their Steam Group and servers they run cuz the posts just decay after a few days and nobody see's it

so generally you might be better off just doing a google search for 8 player L4D2 Servers / Groups and see if anyones websites that talked about it might have links to a steam group etc.

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(For more info on server selection see the How to Select a Server guide, or theres a video explination Here,[twitch.tv] but its not very good so id still suggest reading instead lol its probably faster anyway)

So hopefully this is helpful to players that want to know what theyre getting when starting a match and especially on workshop (custom) campaigns, so get out and slay some zombies with your friends lol and be sure to have fun!

Dont forget the most important thing in L4D2 is to have good friends you can trust to watch your back while your watching theirs! (well at least in expert it is lol)

   
Click Here for the "L4D2 Game Info" guide for players.