In commander format, your deck consists of 99 different (except for basic lands) cards + 1 commander (legendary creature), which defines the colours you may play in your deck.

There are 2 main formats :

• cEDH = multiplayer (4 players mostly, but 3-5 is OK), start with 40 life
  • rules: https://mtgcommander.net/
  • decklists
    • http://mtgtop8.com/format?f=cEDH
• DC (Duel Commander) : one-on-one, start with 20 life (like most of other formats)
  • rules: https://www.mtgdc.info/
  • decklists
    • http://mtgtop8.com/format?f=EDH

Links

• Commander Spellbook: The Search Engine for EDH Combos