I love it when someone asks a writer what genre they write - and the response is "YA" or "MG"
YA and MG in and of themselves are not genres. It is an age category, as is state on wikipedia. (Yes I know it is not the greatest source ever, but it works for me.)
Imagine I am a potential reader. I am terrible at remembering names and titles, not to mention my short comings as a speller. I meet you at your sons fifth birthday party and we get to talking. I find out that you write and have published a few books. Excitedly I ask what genre you write (so that I can look you up). To which you reply, YA.
The next day I go to the bookstore thinking to myself, I want to read that one persons books that I met at the party yesterday. So I head to the (massive) YA section. There are three decent length shelves with YA books filling every inch. They are subdivided into category (such as contemporary, sci-fi, and fantasy). I ponder to myself - what kind of YA did they write? Well I remembered that the book had something to do with a rose, or the title was rose or something. And the authors name was Something Somethingson.
Bravely I start at one end of the first shelf and start browsing. By the end of my journey I have picked up three books to purchase. None of which are yours.
Consider for a moment if you had said - I write YA Urban Fantasy. That is say two little sections of shelf in the book store. Again I leave the store having bought three books - this time all yours.
When someone asks what genre you write - they want to know specifically, in fact I wouldn't mind if some responded like this:
I write upper middle grade fantasy books that mostly feature magic and/or dragons and are set in medieval like worlds.
What genre do you write