Finished goods are goods that have completed required manufacturing process and are ready to be fitted/mixed/processed with final product. The final product itself could also be called finished goods. Examples: cars, clothing, food, furniture 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".