In "Macbeth", what might the witches' predictions about Banquo mean?
They're elliptical, weirdly-worded prophecies, aren't they? The witches say that Banquo will be
Lesser than Macbeth, and greater.
Not so happy, yet much happier.
Thou shalt get kings, though thou be none.
So all hail, Macbeth and Banquo!
What does it mean? Banquo, politically will not be as great as Macbeth, or as financially "happy" as him: Macbeth becomes king, and Banquo stays at his current status - just as a nobleman. Yet - and this is the point - Macbeth is miserable, worried about his crown, and, more to the point, damned to hell because of all the blood on his conscience and on his hands. Banquo dies, admittedly, but he dies noble, good and innocent. He's done nothing wrong. Macbeth dies "a dead butcher".
And lastly, Banquo will father ("get" means "beget" - father) kings, though he will not be king himself. This - as the eagle-eyed reader always points out - doesn't happen in the play: Fleance escapes, but it is Malcolm (son of Duncan) crowned at the end. Fleance, historically, would have been a grandfather or great-grandfather of James I, the sitting king when "Macbeth" was written. So - the audience would have known - that eventually that prophecy would come true. The truth of it was sitting on the throne of England when they first watched the play.
Hope it helps!