Hashtags? QR codes? What??

I feel old.

Because I do not understand the purpose of Twitter. I do not know how to Tweet, I do not get why it’s a viral phenomenon, and I have no clue what a hashtag is.  I keep hearing it everywhere.  I keep seeing it everywhere.  I don’t get it.
I thought this was the extent of my “feeling old”-ness.  I was wrong.  Now I want to know what these QR codes are.  What is the purpose? I’m seeing THEM everywhere too.
I feel like my parents when I say this, but this technology stuff is moving TOO fast for me!  I need to start reading up on all of this before I’m lost forever behind the curve!  I’m just proud I know how to use my iPhone, and I’m blogging.
Baby steps…that’s all I can do!