what are we typing?!?

I have wanted to write about this forever now...What in the world are the words we type in for writing a comment and posting it on someone's blog? I have been wondering, are they all words? They are just random letters put together right? Are any of them words? If they aren't words, why not? Is it someone's job to sit there and think of the crazy word or letter combinations? Has anyone ever got the same word before? I don't think have ever gotten the same code/word to type in. Is that what it is? A code? Why a combination of letters and not numbers? Do some of the other ones out there have letters and numbers? why is the shape so messed up? IT DRIVES ME NUTS!