As noted above "temporary" does not mean "not full-time" it means "not permanent".
There is another difference between "employment agency" and "temporary employment agency" (temp agency) that has not been mentioned.
At least in the U.S., the temp agency itself employs the worker and is responsible for salary or wages, taxes, benefits, etc. The worker is then contracted out to a business that needs a worker for some period of time but does not want to hire its own permanent employee.
An employment agency, on the other hand, generally helps the company to find a worker and the worker to find a job, and charges a fee for that service. The continuing employment relationship is between the business and the worker; the agency is now out of the picture.
The difference between working for a company directly, and temporarily working at a company while formally being the employee of a temp agency is fraught with practical and legal implications.
