I have always wanted to work in stand up comedy just don't know enough about it to do it
I'd love to help you learn about it! One of the most important qualities you need to have as a stand-up comic is the ability to perform in front of a live audience, ideally you want to speak directly to them. 
Oh that would be intimidating to me do a lot of performers have anxiety or stage fright?
I think they probably have to learn how to overcome it. A lot of stand-up comedy is performed in bars, pubs, theaters and comedy clubs, so there's really no escaping the audience!
Is stand up comedy well recieved for the most part?
For the most part it is. Stand-up comics are expected to deliver a steady stream of laughs, so if the crowd isn't laughing, you might want to change up your jokes!
I noticed some stand up events are huge and televised and some are smaller
That's true too! Stand-up is often delivered on television, DVD or the internet. Maybe you'd want to try a few YouTube videos to test your content?
I have heard of open mic night but not sure what that is?
Open mic
An open mic or open mike (derived from the expression "open microphone") is a live show at a coffeehouse, nightclub, comedy club, strip club, institution or pub at which audience members who are amateur performers or professionals who want to try out new material or plug an upcoming show are given the opportunity to perform onstage. Typically, as the name suggests, the performer is provided with a microphone which is plugged into a PA system, to make the individual's performance loud enough for the
in Pasadena, California for several years. He also taught comedy traffic school for five years.
When asked when he knew he wanted to be a writer, he stated, "I thought it happened when I was in high school. But apparently I'd written and talked about being a writer since I was about five. I just don't remember it. Back then I thought I wanted to be an actor and a stand-up comedian. I've done a little of both and want to do more.