An implant-supported denture is a type of overdenture that is supported by and attached to implants. A regular denture rests on the gums, and is not supported by implants. Implant-supported dentures are used when a person doesn't have any teeth in the jaw, but has enough bone to support the implants. An implant supported denture has special attachments that snap onto the implant attachments.
Implant-supported dentures are usually made for the lower jaw as normal dentures tend to be less stable there. Usually a normal denture made to fit an upper jaw is quite stable on its own and doesn't need the extra support offered by implants. However, you can receive an implant-supported denture for either the upper or lower jaw.