what is a blog?

So I find a blog means:
an online diary; a personal chronological log of thoughts published on a Web page; also called weblog.
but as I remember from childhood, my sister would shatter glass if she caught me or one of her two other brothers anywhere in a five foot radius of her diary.  Aren't diaries private?  So I find diary means:
usually private, esp. of the writer's own experiences, observations, feelings, attitudes, etc.
Ah, so a diary is usually private.  It seems to me that a blog is not a diary, because it lacks an attempt at secrecy.  It actually resembles the opposite. No one writes a blog to express their inner most feelings for no one to hear.  Blogs are more like a cyber venting session.  So I find vent means:
expression; utterance; release: to give vent to one's emotions.
Ugh. "To release one's emotions?"  This is more accurate and against a major characteristic of mine, but luckily its not the only meaning of vent I found:
the anal or excretory opening of animals, esp. of those below mammals, as birds and reptiles.
Ah, that's better. What comes from the excretory opening of animals? Poop. What comes out of the minds of a bunch of bloggers? Poop. What's coming out of my mind right now?  Po...psicles.  Popsicles. yep. Popsicles of Inspiration! or POIs.
PS. One fun fact about my family. No matter what the conversation starts out with, we always seem to talk about bowel movements. OK enough, I'm starting to gross myself out.  
PSS. Is it possible to make a Vlog? A video blog? Probably more work but I've got a pal who runs one and a picture is like a thousand words, and there are 30 frames per second so he's cranking millions of words a post!  Just a POI before I head off to bed.