A mechanic is a person who uses tools to repair things (generally machinery) or works to keep things operating properly.
Many mechanics are specialized in a particular field such as auto mechanics, boiler mechanics, industrial maintenance mechanics (millwrights), air conditioning and refrigeration mechanics and aircraft mechanics.
Mechanics possess many skills in technical, electrical/electronic and other vocational areas. Being a good repair technician is more than just "fixing things". A good sound repair requires troubleshooting skills which at times requires the tech to teach themselves how a particular system operates; often in a timely manner.
