I know pretty much everything about command blocks, except for specifiers. I know a few, but could anybody please make a list of them all? I'll put the ones I know here.
r=<number> - Looks for anybody in range of the number.
rm=<number> - Looks for a player at least a certain number of blocks away.
l=<number> - Looks for a player with at least the amount of levels as the number.
lm=<numer> - Looks for a player under a certain level.
m=<gamemode> - Looks for anybody with a certain gameode.
c=<number> - Picks a certain amount of players.
<x>,<y>,<z>[,<r>] - Looks for anybody with the right coordinates. (There needs to be r or rm after that.) EDIT: team=<team name> - Looks for anybody on a certain team.
team=!<team name> - Looks for anybody not on a certain team.
EDIT 2: score_<name>=<number> - Looks for anybody over a certain score.
score_<name> = <number> - Looks for anybody under a certain score.
They're stuff used in command blocks. When there's @a in a command, you can use a specifier at the end of the command. You use the square brackets ( ] and [ ) outside the specifier. You can also use testfor and use a comparator to get an output.
rm=<number> - Looks for a player at least a certain number of blocks away.
l=<number> - Looks for a player with at least the amount of levels as the number.
lm=<numer> - Looks for a player under a certain level.
m=<gamemode> - Looks for anybody with a certain gameode.
c=<number> - Picks a certain amount of players.
<x>,<y>,<z>[,<r>] - Looks for anybody with the right coordinates. (There needs to be r or rm after that.)
EDIT: team=<team name> - Looks for anybody on a certain team.
team=!<team name> - Looks for anybody not on a certain team.
EDIT 2: score_<name>=<number> - Looks for anybody over a certain score.
score_<name> = <number> - Looks for anybody under a certain score.
Anyway, there's team=<team name>, and something like team=<!team name> for all players not on the specified team.
They're stuff used in command blocks. When there's @a in a command, you can use a specifier at the end of the command. You use the square brackets ( ] and [ ) outside the specifier. You can also use testfor and use a comparator to get an output.
I win.
Hope I helped!