Twitter, e-mails

I still don't get how to use Twitter. I have an account but not sure what is it about. One thing that looks similar to tweets are (EOM) e-mail messages I often use at work, but it is still different because it has a TO list.

I guess this is a first sign that as new technologies appear, I will not get some of them and eventually I would need to have something like my grandmother is using, a cell phone with big buttons and no usable SMS function.