The pap smear is another name for the Papanicolaou test, named after Dr. George Papanicolaou, the Greek pathologist who invented the test and published it in 1941.
This test actually has a reasonably high false positive and false negative rate but is still very usable as part of a screening program for cervical cancer. Because of its inadequacy by itself as a gold standard diagnostic tool, all pap smear results (positive, negative or whatever) should be discussed with a doctor.
Current recommendations are for women to have regular pap smears about every two years or so, starting after they have become sexually active.
It takes a whole lot of pap smear tests on normal women (hundreds to thousands) to find one woman with true early cervical cancer but so far it has been deemed worthwhile on a societal scale.