Can anybody tell me what Tumblr is?

I might not be an expert on this things but it is basically a place where you can create blog(s). I for one have 2 blogs in tumblr because i discuss different topics in it. You post your entries much like posting in twitter, but with a few "twists." One, you do not have a limitation of 140 characters unlike in twitter. Next, you can do anything to your homepage/blog just about anything since it is really a blog. And last time i checked, which was late last year, it offers this "thing" that allows you to post in multiple sites (don't know the term), once you enroll it or something like that. For example, when i post to my tumblr account, it would automatically post to my twitter and facebook accounts. I am not sure if there are other available sites where you can do that, but as of now, i am just sure about those two sites.

Tumblr is a blogging platform like BlogSpot, WordPress, HubPages, Weebly, Vox, Webs, etc. You are free to open an account and then, publish stuff you want. Don't you have a blog?