Commander is a series of supplemental Magic: the Gathering card game products. Its mechanics are derived from a fan-created format known as "Elder Dragon Highlander". The official Commander format is "the only sanctioned format maintained by an outside entity" other than Wizards of the Coast.

What is considered a commander MTG?

When choosing a commander, you must use either a legendary creature, a planeswalker with the ability to be commander, or a pair of legendary creatures or planeswalkers that both have partner. The chosen card or pair is called the commander or general of the deck.

Is Commander a standard?

Technically, it's just a Constructed format with some particular rules that set it apart from things like Standard or Modern. You use a 100-card deck, including a legendary creature that begins the game in your command zone rather than your library.