A "Type Certificate" is the way the FAA approves the design of an aircraft propeller or other major aviation -related product. A type certificate authorizes a manufacturer to make the product in the specific way covered by the certificate. If the manufacturer wants to make a major change to the design of the product, approval from the FAA must be obtained. In these cases, the FAA issues a "supplemental or amended" type certificate. To look up a specific Type Certificate for your aircraft, they are available on the FAA website - Type Certificate Data Sheets.