This page contains information about the types of tournament brackets that will be used for the APA of Philadelphia.  There are 3 formats:  Single Elimination, Modified-Single Elimination, and Double Elimination
Single Elimination:
As the name implies, this is a type of bracket where the loser of a match is immediately eliminated from winning the championship or first prize in the event. 
Modified-Single Elimination:
A compromise between Single and Double Elimination.  Players can lose their first or second match & are still eligible to win the championship or first prize in an event. Every player/team is guaranteed to play twice, but not guaranteed to lose twice.  (If you lose both your 1st and 2nd round - you are eliminated.   You can lose the 1st OR the 2nd match, and still be eligible to win.  If you lose a single match after the 3rd round, you are eliminated)
Double Elimination
A competition in which a player/team has been eliminated upon having lost 2 matches.