Most agencies specialize by the type of Talent they place. Larger staffing firms will have divisions that specialize in many different areas. Some work in niches narrowed by industry as well as position type. For example there are companies who only place people experienced in corporate accounting. While others will specialize in placing accountants with public accounting firms.
Staffing or temp agencies may specialize in placing customer service representatives or administrative assistants and clerical workers. Others specialize in health care or IT.
There are also companies that specialize in light industrial positions such as assembly or warehouse work. And then there are day labor companies. The list goes on and on.
Staffing companies also offer different
types of placement.
Some staffing firms are full service agencies, meaning they offer direct placement as well as placement on a temporary-to-hire or a temporary basis. Some companies only place people on a temp-to-hire or temporary basis. And others only offer contract employment.
Most headhunters or executive recruiters only place people on a direct hire basis. There are many hybrids and variations out there.
Top staffing agencies will have job openings you won’t find anywhere else. At the company I owned we had clients who only hired through us. The hiring authorities trusted that we understood what they were looking for, would screen appropriately, would respect their time and make it easy for them to hire. Which of course we did.
A few even went so far as to refer people who applied to them directly, back to us for screening. They knew that if the applicant could get through us s/he was worthy of consideration.
On the flip side, other agencies only have openings being worked by many other recruiters. Some hiring companies will give an opening to any staffing person who calls. Since there are so many recruiters working the positions, it is rare that any of them get much (if any) of the hiring manager's time.
Generally these easy to get openings are hard to fill for one reason or another. The job function is undesirable, the pay is substandard or the combination of skills and experience sought are impossible to find. Sometimes the work environment is difficult to take. Or the company's hiring process puts up so many road blocks they can't hire effectively.
My staffing agency wouldn’t touch these openings because we were determined to place the talent we represented into good situations. But there are a surprising number of staffing or temporary companies that do take them.