"Enters the battlefield" refers to putting a permanent onto the battlefield, or to an ability which is triggered when a permanent is put onto the battlefield. It is commonly abbreviated ETB.
"Enters-the-battlefield" abilities are a mechanic designed by Bill Rose for Portal. The design team liked it so much that they included it on one card of each color in Visions. Popular cards with "enters-the-battlefield" effects were Nekrataal and Man-o'-War.
"Enters-the-battlefield" abilities which damage or kill a creature or destroy a permanent were colloquially known as 187 effects.
- Enters the Battlefield
- A nontoken permanent “enters the battlefield” when it’s moved onto the battlefield from another zone. A token “enters the battlefield” when it’s created. See rules 403.3, 603.6a, 603.6d, and 614.12.
- 603.6a Enters-the-battlefield abilities trigger when a permanent enters the battlefield. These are written, “When [this object] enters the battlefield, . . . “ or “Whenever a [type] enters the battlefield, . . .” Each time an event puts one or more permanents onto the battlefield, all permanents on the battlefield (including the newcomers) are checked for any enters-the-battlefield triggers that match the event.
- Brady Dommermuth (June 01, 2009). "Mechanically Inclined". magicthegathering.com. Wizards of the Coast.
- Mark Rosewater (June 5, 2017). "Mechanical Color Pie 2017". magicthegathering.com. Wizards of the Coast.
- Aaron Forsythe and Mark L. Gottlieb (June 10, 2009). "Magic 2010 Rules Changes". magicthegathering.com. Wizards of the Coast.