It is more like a micro blogging platform with an integrated RSS Reader.
My tweets are my blogs entries limited to 140 characters.
Clicking on followers is the same as clicking on subscribe to another blog RSS.
When I view all my followers tweets, that timeline is exactly like me viewing all my subscribed RSS in an RSS reader, the only different is you see the content there and then rather than clicking a link to view the entire story.
Retweets is same as reblog button on a blog.
Reply to a tweet is same as making a comment to a blog post.
As for Facebook I don't have an FB account to know how it functions. I'm guessing if you think about it long enough it is close to being a blog too with more bells and whistles. Adding your family/friends is akin to subscribing to their feed is just like subscribing to RSS on a blog.