Just wondering, if this is possible ? @ send Topic

Is it only me confused by this question and answer?

How is opening the Composer via a link the solution to “opening a Topic”? (which suggests the Topic already exists)

And what is meant by “@ send” ing something? This is not clear to me at all. Am I missing some ‘lingo’? What is an example of @ sending on another platform?

Or could the question be phrased better?