Do I really understand these social networking

tools on the internet? I do not think I understand them at all.
There is this blog - a random set of cat hairs which is just held together by something (although I am not sure what that something is) and there is Facebook and there is Twitter. I suppose if I was really interested in such things there would be other things as well.
I do not put much up on Facebook, just the occasional comment. What it does is keep me informed about the writing activities of a few individuals. I am not going to post photographs of myself there - or here, or anywhere else. (You might get the mistaken impression that I am human!)
Twitter still puzzles me a little. There are hash tags and so on that I have still not managed to work out. Is it polite to send messages to people you follow out of interest but who do not follow you in return? Would I even dare to send a message to them? Probably not. It is not that I follow any 'celebrities'. I am not interested in celebrities. I like writers. Writers are not celebrities. Most of them are much too sensible for that. Writers get on with life. They have to live two lives, their real one and their writing life. It does not leave time to be a celebrity.
Twitter however seems to work in an odd sort of way. I woke up this morning and found three new 'followers' in my mail box. I have never met any of them in real life. I may never do so. One of them writes a very interesting blog (with the help of margarita drinking beagle). I will investigate the others and find out who they are as well.
You get a mere 140 characters for a message on twitter. It amuses me that our politicians are very bad at this. They seem to mostly have given up on Twitter. I suspect that this is because there is just not enough space for them there. On the other hand good writers can get a message across in even less characters.
I do not twitter or tweet like a bird. I prowl - mostly in silence. There is a lot to be learned by observation.