There’s nothing more annoying than being a couple of pages into a book and still have no idea where the story is taking place. I don’t need to know the exact geographical coordinates, I don’t even need to know the city the characters live in, I just want to be able to picture them somewhere.
It’s called settting the scene.
And it’s important to do it from page one. The reader needs to feel like he’s right there in with the characters so he feels compelled to keep reading.