An operator is a person who runs a machine, equipment, or a vehicle. If you want to be a jackhammer operator some day, you might hope to work on a road crew of for a construction company.
An operator operates, or controls, something. You could be a radio operator, a heavy machinery operator, or even a telephone operator — or you can be the operator, or manager, of a business. If you start your own dog walking company, you can call yourself an "owner-operator." The Latin root of both operator and operate is operari, "to work," and "to cause."