Something that's unsettled is out of order or unstable in some way. If you've just moved and started at a new school, your whole life may feel unsettled.
An unsettled situation is tumultuous or uncertain, and an unsettled person feels uneasy. You'll feel unsettled if you hear your best friends fight bitterly, or if you hear creepy noises coming from the attic late at night. If something hasn't been resolved yet, you can also describe that as unsettled: "The question of who will go pick up the pizza remains unsettled."