Really isn't anything like you're askin' for, really; sorta hard to do for a site with nearly 20,000 members and close to a million articles, some in threads thousands of replies long, and adding to the list every day.
There are folks here from everywhere ... all over the world, literally, from Alaska to Australia, from London to Tokyo. I'd say the "agegroup" runs from 'teens to eighties, though I'm sure there are both younger and older ones here and there from time to time.
About the only thing you should "Know" is how things work around here. For a shortcourse in that, if you click on the color-formatted links down at the bottom of any of my posts, you'll find the A2K FAQ, which answers lots of basic "How To" questions, the A2K Help Forum, which is the place to ask for specialized help with A2K features and functions, and the A2K Terms of Service, which pretty much is the law around here. That boils down pretty simply; keep it civil, no spam, porn, gratuitous vulgarity, hatespeech or personal attacks/flame wars. Poke around some and enjoy exploring the place ... and don't worry, you can't break anything.
In the meanwhile, here are a few threads you might want to check out, to sorta get "The Lay of The Land" and start to get to know "Who's Who".
Welcome to the New Members A place the new folks get a chance to meet some of the folks who've been around a while longer
How Did You Come to Know About This Site Lots of folks have told how they found this place, and told a bit about themselves
What Made You Smile Today A nice chatty thread frequented by lots of regulars here, the title pretty much sets the tone. Good place to get to know folks
Lola At The Coffeehouse Another hangout for lots of regulars