This label is given (incorrectly) to almost the entire recruiting industry.  However, the term applies to businesses whose primary goal is to find a position for an applicant who wants a new position.  They may charge the applicant or they may charge the firm who hired the applicant.  Agencies who charge the applicant are typically working with unskilled applicants.  These firms seem to be dying out.  Agencies who charge the firm hiring the applicant are today the most popular and come in all sizes, shapes and colors; for example, there are national agencies such as 'APPLE'.  Agencies specializing in a particular field or industry such as temporary help, insurance, aerospace, nursing, doctors or computers.  Their method of operation is to find a person who is looking for a position and then conduct a telethon of known firms who hire this type of person, soliciting interviews until the applicant is hired.