I have been asked this question a lot and so I thought I should create a short post answering it.
It is fairly simple and therefore this post will be fairly short!
Question: What does .@ mean in Twitter?
Using ".@" in Twitter doesn't mean anything.
".@" on Twitter is used as a public reply, as opposed to replying individually to a user, using their @username.
In order to get around this, as well as to make your reply visible to all your followers (not just those in the thread), you need to prefix the tweet with something so it doesn't start with the "@" symbol.
Otherwise, it tries to link to a specific username.
The most common solution became ".@".
That said, any character can be used but people chose to use ".@".
This was probably because it's both easily accessible, as well as the fact that its the smallest symbol on a keyboard.
And that's it!
Did you have any other questions regarding Twitter? Let me know down below!