The DEL is the top-tier professional league in German ice hockey, and it currently has 14 member teams: EHC Red Bull München, Adler Mannheim, Thomas Sabo Nürnberg Ice Tigers, Kölner Haie, Grizzlys Wolfsburg, Augsburger Panther, ERC Ingolstadt, Eisbären Berlin, Straubing Tigers, Fischtown Pinguins Bremerhaven, Düsseldorfer EG, Schwenninger Wild Wings, Iserlohn Roosters, and the Krefeld Pinguine.
A season is divided into two parts: the regular season and playoffs. During the regular season, all 14 clubs play against each other four times. Each team plays 52 games. The rankings at the end of the regular season determine which teams advance to the playoffs. Teams in 1st – 6th place qualify directly for the playoffs. Teams in 7th – 10th place compete in pre-playoffs for the remaining two playoff spots. In the end, a total of eight teams qualify for the playoffs. For the rest of the teams, the season is over.
The rankings determine who plays against whom. In the quarter-final, the first-place team plays against the eighth-place team, second against seventh, third against sixth, and fourth against fifth. A team wins the round and advances after beating its opponent four times (best-of-seven format). A match between two teams can last between four (four wins in a row, 4:0) and seven games (team wins the round with four wins and three losses, 4:3).
Teams generally alternate between playing at home and away, but the team with the higher regular-season ranking has the right to play at home for Games 1, 3, 5, and 7 (if necessary), so it always starts the playoffs in front of its home audience.
The rules are explained (in German) more fully here, with examples from the 2016/17 season.