On several StarCraft II pro-gaming websites I read about "seeds" being invited to tournaments. What exactly is a "seed" as far as gaming tournaments are concerned?
Knockout tournaments of any type traditionally use a seeding system. This is to prevent the 1st and 2nd ranked players from fighting until the final, the 1st,2nd,3rd and 4th from meeting until the sem-final etc.
Depending on the tournament structure the number of seeds will vary. The top 16 players or so are ranked as "seeds" and the tournament is drawn up by seeding the programme with these seeds before adding in all non-seeds in a random order. In Tournaments with a number of participants which isn't a power of 2, some number of players starting with the top seeds will be given a "bye" and avoid playing in the first round. This gives a power of 2 number of players in the 2nd round.