A recruiter is someone whose job involves signing people up as members or hiring them for jobs. Sometimes company recruiters visit college campuses to talk to interested students.
A recruiter for a large company might place advertisements for job openings and interview applicants, while a military recruiter works at an office where interested enlistees can sign up to join the armed services. If you work as a recruiter for your school's French club, it's your job to make the club look exciting and fun, and to sign up new members. The origin of recruiter can be traced back to the Latin crescere, "to grow."