A sticker is a label or a decoration with a sticky back, so it can be pasted anywhere. If you're a big fan of superheroes, you might cover your notebooks with Wonder Woman stickers.
Sticker usually refers to the kitten stickers your brother sticks on his bedroom windows or the adhesive labels that you peel off your banana. Some plants also have stickers (also known as burrs, prickles, or thorns) — the kind that get stuck in your sweater after a walk in the woods. The term sticker price means the listed price for a car or some other item offered for sale.