So I'm making a kind of kit PVP game called classes, where you join a team, let's say, the barbarian. You can't hit any other barbarians, and it shows everyone else with the same class. But I want people with certain classes to have special effects how do I do that?
I tried:
/effect 1 1000000 5 @a[barbarian]
But it didn't work. I am running 1.9
Selector parameters consist of a unique key name and a value, separated by an equals sign, with each unique parameter separated by a comma. The team parameter is what allows you to target players based on their team. For the /effect command, the target comes first:
/effect <player> <effect> [seconds] [amplifier] [hideParticles]
/effect @a[team=barbarian] minecraft:speed 1000000 5
See also, Minecraft Wiki: Target selector arguments.
/effect @a[team=teamname] 1 1000000 5 would set an effect to all players on a certain team, where teamname is the name of the team that you want to give the effect to.
http://minecraft.gamepedia.com/Commands#Target_selector_argumentswould have told you what you were doing wrong.