I’ve used some rapid at home antigen tests. That is what you are most likely being offered. An antigen is a part of the virus that can bind to an antibody. So it’s a test that detects the virus.
These are not the painful kind. You put a swab about 3/4" inside a nostril and rotate the swab.
No big deal.
There may be recommendations coming to swab the throat instead, but that hasn’t happened yet in the US.
The more definitive test given at official testing sites is a PCR test, which tests for the viral DNA. It involves sticking a swab much farther up the nose – it made my eyes water when I got one. Definitely uncomfortable. But, more accurate.
The at home rapid tests used to be more than 90-95% accurate if you were having symptoms but less accurate for non-symptomatic testing. Now, they may be even less accurate as they are less sensitive to Omicron.
It appears that they may be better at detecting Omicron if you swab your throat. Apparently some countries (the UK I think?) have provided instructions on how to swab the throat.
I had that test several times last year, as I required a test every two weeks to visit my mother in her retirement residence. Like getting a needle or having blood drawn, the experience varies depending on the skill of the person doing the swabbing. I had some that were pretty unpleasant, and at least one that didn’t bother me much.
We test so frequently in the UK now (all tests are free and on demand), that they’re pretty much all self-administered - even the ones we go to a test centre for. I find self-administered tests much less daunting.
OP, the home tests you are being offered are most likely rapid flow/lateral flow tests, which only require a nasal swab and give you a result in 15-30 minutes. It’s not painful - it’s just sticking an ear-bud like device up each nostril and swilling it around a bit. Might make your eye water, but that’s about it.
This image may be helpful. The PCR molecular tests are the most accurate. The ones through the mail are probably antigen tests, which are not as accurate.