In multi-storied buildings maintenance charges is charged and frequently the word AMC is used.  Please explain the words?

Maintenance means, maintaining the building, machinery, and related common areas in good and working conditions. In the case of apartments it refers to maintenance of common areas, common lighting, staircases, elevators, etc., which are for the common benefit of all the occupants of the particular building.

AMC means, Annual Maintenance Contract.  Association of apartment owners entrust the maintenance of common areas/machinery to an outside agency, terms and conditions for the same are reduced into writing in the form of a contract known as Annual Maintenance Contract.