Who is One Direction?

Okay so for the longest time, my news feeds have been blowing up about some group named One Direction...who are they? Really I want to know and I don't really want to get into the hype about them, they seem too mainstream,but that's my opinion. They remind me of that Big Time Rush group too. The only person that I know from the group is Harry Styles, I think his name is? Someone said he was dating some chick that was like a million years older than him. But really they're all over the place. So someone please fill me in on what I could possibly be missing.