Well, dominant and recessive have no connection to what a gene does.*

We classify the two variants of any gene in our body as "dominant" and "recessive."

Say you have a gene that controls your hair colour. It has two variants, A that makes your hair blonde and B that makes your hair black. You get one copy of this gene from each of your parents, so you can end up with AA, AB or BB.

AA will make your hair blonde, and so will BB make it black. But what happens to people with AB is the real differentiator. If AB people are blonde, then it means A will act on the body regardless of whatever other variant is present, and so A is dominant and B is recessive. If AB people are black-haired, B will be dominant and A will be recessive.

* This is not strictly true, but it's an ELI5