Dribbble is show and tell for designers. Players share shots—small screenshots of the designs and applications they are working on.
What are shots?
Shots are small screenshots (400×300 pixels max) posted by members to show what they are working on. Some have called Dribbble “Twitter for designers.” Shots are to Dribbble as tweets are to Twitter.
What’s a player / spectator / prospect?
A player is a member at Dribbble who can post shots and comments. Players are drafted (invited) by current members.
A spectator is a member who can follow and discover shots and people on Dribbble, but cannot post shots and comments. Anyone can sign up as a spectator to follow the work and people on Dribbble.
A prospect is simply a spectator who has indicated (in their account settings) that he/she would like to be drafted as a player. There is a prospects list to help find these members.
Link: Dribble