All Airports are licensed. It is the job of Airfield Ops to ensure that the license is complied with. The Safety of Aircraft, Passengers, Personnel and equipment are also their resposibility.
Regulation of the ramp. Airfield inspections, Runway inspections. Wildlife management, all come under their remit.
Apron Control who allocate stands to aircraft are also part of Airfield Operations at some airports.
I'm sure people from other airports can add to the list....
There are no special requirements as far as qualifications are concerned. Generally some knowledge of Airports/Airlines is an advantage...All training is done on the job. There are no nationally recognised qualifications although the depth of knowledge required is quite deep and broad. This hopefully will change in the future. There are however, many certificated courses.
Getting into Airfield Operations is a case of checking the airport web sites for jobs be warned though they don't come up very often.