What means level / self / player

Hei guys

Can someone tell me what self / player / level means?
example:
1. level waittill( "connected", player );
2. prestige = player getPrestigeLevel();
3. foreach(player in level.players) ..

and what means this "." between level and players?

level means the level, player means player, foreach(level.players) means for each players in the level