It's not medical it's just a thing. A false positive is when the test says you're positive but upon further review you are not. A false negative of the opposite, the test came back negative, but you really have it. Nobody take about those rates though because it's too technical and inconvenient for narratives on either side. Plus, if the false positive and false negative rates are equal, then the general assumptions based on the data are fine
I've mostly seen it in the cyber security world where they're talking about automated that detection. A false positive is when the system says "oh shit you're being attacked!" But it's just Bob in accounting running a particular once a year job the system hasn't encountered before. A false negative is when the system says some action or internet traffic was benign but it's actually someone owning your servers (or preparing to).