In what kind of situations can you say "Leave It"?! It's UK slang or something?!!?

[♥♥♥♥♥chastity♥♥♥♥♥]

My UK friend on twitter keep using "Leave it" in very weird situations :/ What does it mean and when can you use it? It's some kind of slang?
examples: have never seen a bigger name dropper than Niall from one direction #leaveit
Watching Harry Potter and the Deathly Hallows part 1 #LeaveIt
Westfield doe #Leaveit

[Si Si Paris]

Can you give us an example? The only time I use it is when I'm directly telling someone to leave it there, like an object or something. But I'm from the US.

[Sonal]

it's common everywhere to use that term

[stevesimon006]

sometimes it can mean-"stop talking about it"or "change the subject"
uk here