Blank verse is the technical name for unrhymed iambic pentameter — i.e., verse of five feet per line, with the stress on the second beat of each foot. It’s one of the most common kinds of verse in English: many passages of Shakespeare’s plays are in blank verse, as is Milton’s Paradise Lost and Wordsworth’s Prelude.
Under no circumstances should you confuse blank verse with free verse.
Note: This guide is still in the early stages of development.
Three question marks mean I have to write more on the subject. Bear with me.