Dies

Dies is a mechanic in Magic similar to "destroy" and was reintroduced in Magic 2012 to replace the phrase "is put into a graveyard from the battlefield". The introduction came in anticipation of Innistrad and the Morbid mechanic. "Dies" used to be a slang term for this occurrence before and is now officially used to signify triggers. It is exclusive to creatures while other card types still use the old phrasing.

From the glossary of the Comprehensive Rules (June 7, 2024—Modern Horizons 3)

Dies

A creature or planeswalker “dies” if it is put into a graveyard from the battlefield. See rule 700.4.

From the Comprehensive Rules (June 7, 2024—Modern Horizons 3)

• 700.4. The term dies means “is put into a graveyard from the battlefield.”