What is a Senate filibuster?

A filibuster is a Senate tactic in which a senator (or group of senators) extends debate on a bill to delay or block a final vote. Under current Senate rules, it takes 60 votes to end a filibuster through a procedural vote called "cloture." Because most legislation requires only a simple majority (51 votes) to pass, the filibuster effectively gives the minority party significant power to block legislation.