The short answer
An A&P is an FAA-certificated mechanic holding both Airframe and Powerplant ratings, authorized to perform and approve maintenance, repairs, and 100-hour inspections on civil aircraft. Approving an annual inspection additionally requires Inspection Authorization (IA).
What the certificate covers
The Airframe rating covers the structure and systems of the aircraft; the Powerplant rating covers engines and propeller-adjacent systems. Together they authorize the holder to return an aircraft to service after most maintenance and alterations, with major repairs and alterations requiring additional approvals and documentation.
Owners work with A&Ps constantly, and a mechanic's signature and certificate number in the logbook is what turns work performed into a maintenance record. For owner-assisted maintenance, the supervising A&P remains the one who approves the work.
Related terms and reading
Keep every hour and inspection straight
Maggneto tracks engine times, inspections, and ADs from your actual logbooks — so terms like these become numbers you can act on. Browse the full maintenance glossary.