talking about 2 (or more) types of testing as if they're the same thing. They are not. Most rapid tests that are being hyped are based on the body's immune response to the virus. It says nothing about current infection, but only if your body has produced enough antibody response to be detected. That likely doesn't happen for days (or more?) after you've contracted the virus and your body starts to fight back. So you could be in full blown COVID, but these tests will say you're negative because your body hasn't ramped up the fight yet and even then it may not be in sufficient quantity to register. These tests are typically done using blood and small "kits" that can be purchased all over suddenly.

The only tests considered to be truly accurate (99%+) are PCR (polymerase chain reaction) based, because they're detecting the RNA of the actual virus in your system. These tests can only be run on expensive lab equipment and are mostly done from nasal swabs. This test will come back positive relatively quickly once the virus is in your system and has had a chance to replicate in sufficient number, even if you don't have symptoms.

I know there are a number of local urgent care/family medicine clinics locally that were really hyping their rapid tests for all, and actually had public health come down hard on them and order that they cease since it is only muddying the waters.