Finished goods are goods that have completed required manufacturing process and are awaiting to be fitted/mixed/processed with final product OR final product itself could also be called as finished goods. Examples: cars, computers, spare parts, etc.
In manufacturing there are three different sorts of stuff:
Something bought as a "raw material" is used to manufacture a product. A thing that is not completed during the manufacturing process is called "work in process". When the manufacturing of the thing is completed but it is not yet sold or distributed to the end-user, it is called a "finished good".