If you are selling a piano, you will need to know what a reasonable asking price is. You may also need to know how much your piano is worth for insurance purposes. Valuing your piano's worth is getting an appraisal. An appraisal includes a full inspection of the piano, a written report, and a written estimate, if it is desired by the client. It also includes determining the piano's age.
If you are buying a used piano, you will be spared a lot of problems by having a qualified piano technician inspect the piano before a sale is made. This is a purchase consult. Like an appraisal, it includes a full inspection of the piano, a written report, and a written estimate, if it is desired by the client. It also includes determining the piano's age. However, there are things that you can look for to narrow your choices so you do not end up hiring a piano technician to inspect ten pianos. I sell "How to Buy a Good Used Piano" by William Leverett.
If you would like to know what repairs are needed on your piano and how much they will cost, that is an estimate. Estimates are provided free with appraisals, purchase consults, tunings, or any other service call.