Standard DayZ experience, all official servers follow that pattern. The most characteristic thing about them is that you never know who is your friend and who is your enemy. More popular servers often introduce some rules or changes to make the gameplay fair and engaging. Most common are safe zones or time limited raids.
On that type of server you are not allowed to fight other players (damage from player to player can be often disabled at all). Your goal is to survive in the harsh environment and fight challenges like enhanced infected types, mutants or AI controlled bots. Such servers often introduce traders and reputation system.
This is the most demanding server type which requires lot of patience and fair play attitude. The aim of RP is to engage players into the lore, experience the adventures, tell the stories. You can compare it to a theatrical improvisation, but restricted by many rules changing completely the way you play the game.