I write for young adults. Or you could say I write YA fiction. YA is not a genre, even though some people will talk like it is. The genre I write in is contemporary realism. Which means, it’s set in the present and it deals with realistic situations and characters.
Is this important? It is when I’m pitching or submitting my work, because agents and publishers need to know where my work fits into the larger scheme of things. And if I ever get published *sigh* book stores and libraries will want to know which shelf to put the book on (not the library I visit though. For some reason that shelves fiction in alphabetical order, so it’s a real chore finding the genre you like to read). And readers like to know genre too, so that they have an idea of whether they’ll like the book before they go to all the work of reading it.
Different genres also have different conventions – things that readers will expect to find. Romance needs to have two people trying to find a romantic relationship with each other, History needs to be set in the past. And, of course, there’s sub-genres of genres – Historical Romance anyone? If you say your story fits into a genre and then it doesn’t contain the expected elements of that genre, you’re going to frustrate your readers. After all, I’m not interested in a Romance that skimps on the sexual tension but goes heavy on the detective’s search for a killer.
At the very least, think of genre like the key on a map. It doesn’t give you all the detail, but it’ll give you an idea of what to expect. It’s the ‘Here Be Dragons’ of the literary world.