To put it simply, a fantasy football draft league is a non-continuous league that requires you to draft players at the beginning of each season. Each member of the league is placed into a draft order and required to select players through a draft process. The first person to pick has first choice of all players in the league, and the draft proceeds through every member of the league until everybody has made a selection. The way the draft then continues depends on the type of draft league it is. The draft picks may maintain the order from the first round, as in a straight draft, or reverse order, as in a serpent draft. This continues until each member of the league has a specified number of players at each position or meets the cap for total players allowed on a single team.
After the completion of the draft, every member's team is set and can only be changed in a few specific ways. A member can cut any of his or her players and pick up any player off what is called the waiver wire to replace them. The waiver wire a list is all of the players that went undrafted or have been cut from other member's teams. Draft leagues incentivize this method of picking up and dropping players, especially in times of injury since the team rosters reset after every season anyway.