This has been a question for a while from many people who use/wear this product on a regular basis.
Nail polish is a lacquer (aka varnish, paint, etc). It seems that the usage of the terms “lacquer” and “polish” are based on geography and/or manufacturer’s preference. It’s just a cosmetic used to decorate the nails on both hands and feet.
They come in multiple shades and styles and textures. Some of the more common styles are matte, glitter, metallic, shimmer, and high gloss.
In addition to decoration, the formula has other benefits when applied such as providing a stronger, chip resistant coating to the nails.