[Pawno_Master]

https://sampwiki.blast.hk/wiki/SetPlayerTeam

Here you can find related functions aswell.
You can also create your own function!

new PlayerTeam[MAX_PLAYERS];

if(strcmp("/grove", cmdtext, true) == 0)
{
PlayerTeam[playerid] = 1;
SendClientMessage(playerid, 0xFF0000AA, "You are now a member of Grove Street!
}

EDIT: Here a list with all functions

https://sampwiki.blast.hk/wiki/Category:Scripting_Functions