What is a seeded Tournament?
A Seeded tournament is organized in a way that teams are (commonly) ranked based on skill level, experience, and/or previous accomplishments. Ranking for the purposes of seeding in an Xfire tournament is ultimately decided by the tournament admin. The match ups are then determined off of the rankings set by the admin.
How does seeding work?
Seeding is fairly straightforward and the matches placed on the brackets are always done the same way so long as the seeding order is the same. Seeding is designed to create the best possible matches in the final rounds of a tournament by giving higher ranked teams a better shot at making it into the finals.
In the diagram below you can see this clearly illustrated as the top ranked team (Alpha) is matched with the lowest ranked team (Omega), the 2nd highest ranked team (Beta) is matched with the 2nd lowest (Theta), and so forth until all teams are matched up (the final match up resulting in a match between the two middle ranked teams.) Furthermore you will notice that the higher ranked teams are placed on opposite ends of the bracket further increasing the chance of the final bracket rounds consisting of matches between highly ranked teams.
In the case of a tournament that does not contain a "perfect" amount of teams to fill all of the first round brackets, the highest ranked teams will automatically receive a bye (a pass into the next tournament round).