A banneton is a basket used to support a shaped loaf during proofing. It may be lined with cloth or left bare to imprint a pattern; flour helps prevent sticking. Round baskets support boules and oval baskets support longer loaves.
Turn the dough onto its baking surface before baking. A banneton is a proofing aid, not an oven-safe baking pan. Brotform and proofing basket are common related names.
Reference: Further reading.