The numbers generally indicate both the manufacturer and the specific product. The UPC Codes for a 6-pack of strawberry yogurt, a single strawberry yogurt, and single blueberry yogurt from the same manufacturer would all be different.
A UPC Code does not carry any price information. When the code is scanned, a store's computer will check that product against the current price stored in its database. This allows stores to set their own prices.
Sponsors sometimes require a UPC Code from one of their products in order to enter sweepstakes. See How to Find Free UPC Codes for more information about entering these kinds of sweepstakes without purchase.