Thanks to a lot of very old, very famous white guys, blank verse is one of the most common forms of English poetry. Oh, and we should say—it's anything but blank. The term refers to verse that has no rhyme scheme, but does have a regular meter—iambic pentameter, to be exact.
Why is blank verse so common in English? Well, a lot of people think we speak in blank verse in our everyday conversations. Kind of like we just did: "a lot of people think we speak in it." That could be a blank verse line.
This verse was common in Renaissance dramas by folks like Shakespeare and his frenemy Christopher Marlowe, both of whom made the verse accomplish all kinds of amazing fancy feats. But it's used all over poetry, perhaps most famously in Milton's Paradise Lost. Traditionally, blank verse is used when the writer is tackling serious subjects, and you don't get much more serious than Satan.
Remember, though, blank verse isn't just for poetry. Be sure to check out blank verse in some of Shakespeare's plays, too, like The Tempest.