What happens when u @ someone on twitter?

[Jessica]

What happens when you @ someone who's not following you? How can you get someone's attention on twitter that's not following you

[Misunderstoodbook693]

Well, it kinda works like this -
Let's say user A follows user B, but user B dowsn't follow user A. User A wants to hit up a conversation with User B, so he tweets him:
"@UserB hi"
That tweet will show up in User B's "Mentions" section, regardless if he's following or not. These tweets will show up in "Mentions" unless you've blocked them, or (maybe) if they have their tweets set to "private."
The only ways to get someone's attention on twitter are:
-following them
-retweeting them
-replying to various tweets of theirs