Regular Polish and UV lamps

Can't find the answer online, wondering if anyone here knows.. Before gel was everywhere, I always got acrylic nails. They painted my nails with regular polish, I put them under the UV lamp for a couple layers, then boom, all dried and perfect and no worrying about smudging. Then stopped getting my nails done for a bit.

Now, I've gone into the salons and everyone tells me the UV lamps are for gel nails only, regular polish needs to air dry. Which makes sense, but then, what was I doing before? Was I getting a special nail polish or something? Because it was all dried instantly. I can't figure it out!