What’s PCOS?

So I was wondering.. what is PCOS? I heard a few people say “I got

Diagnosed with PCOS.” Just wondering..

Update:

Thanks for the comments, so what are you supposed to do if you think you have them .. make a doctors appointment? Or start a diet? Are you suppose to loose weight? Do the doctors give you medicine?

I have a feeling I might have them because I gain weight really fast, and may face hair grew more and the hair on my head has gotten less.. I’m a bit stressed .. thanks for the comments tho ♥️