What does a false-positive test result mean, in words, in this context?

Cancer

The value of mammography as a screening test for breast cancer has been controversial, particularly among young women. A study was recently performed looking at the rate of false positives for repeated screening mammograms among approximately 10,000 women who were members of Harvard Pilgrim Health Care, a large health-maintenance organization in New England [9].

The study reported that of a total of 1996 tests given to 40- to 49-year-old women, 156 yielded false-positive results.