OpenDecklists
Open Decklists is a project to help Magic players find and learn decks and formats
Standard
Standard is a changing format that includes the cards printed in the most recent 3-ish years of set releases.
Pioneer
Pioneer includes cards from standard set releases since Return to Ravnica (2012) and forward.
Modern
Modern includes cards released in standard and horizons sets since the modern frame was created in Mirrodin in 2003.
Magic Theory