Inlays are called indirect restorations, because the restoration is fabricated outside of the mouth, instead of being built in layers directly into the teeth like a filling. The dentist takes impressions of the teeth, then the restoration is shaped to match the part of the tooth it will replace. The restoration is attached with dental cement.
An indirect restoration is an inlay if it covers part of a tooth, without extending to a cusp, and may be made of ceramic or gold.