“What is twitter all about?” is a regular question twitter user have to answer, because they are using it. En gross it’s about getting and sharing information, whereas that information is most of the time low of quality.
So the question arises again: “What is twitter all about, if not just spending your time randomly?”
Well, you could answer, twitter was one of those things in life, where the question of its sense can’t be put in one single sentences, whereupon this wouldn’t mean there was none. It just would lie in its potential to use it. This is a quite philosophicla answer and hard to criticize as it goes down to the argument: Having something with a possible usage is better than not having it at all.
But sometimes twitter is good to explore yourself and getting information about your own in a sort of soliloquy:
How good you can share these new knowledge achievements to the world.