'Evoke' was introduced in the Lorwyn block and it currently appears on a number of cards including Briarhorn and Cloudthresher.

702.71. Evoke

• 702.71a. Evoke represents two abilities: a static ability that functions in any zone from which the card can be cast and a triggered ability that functions on the battlefield. "Evoke [cost]" means "You may cast this card by paying [cost] rather than paying its mana cost" and "When this permanent enters the battlefield, if its evoke cost was paid, its controller sacrifices it." Paying a card's evoke cost follows the rules for paying alternative costs in rules 601.2b and 601.2e-g.

Translation:

• 702.71a. Evoke, in the game rules, means two things. It provides the alternate casting cost with which to play the spell. And then it has the triggered ability that when the spell is played for that cost, to cause the permanent to be sacrificed.