ELI5: With how effectively Reddit is shaping the world around it, exactly HOW big is Reddit?

I came across reddit not too long ago, and thought it was a great place to get a quick laugh. As the months progressed, I found that there was actual INTELLECT here, and I could actually engage in a decent conversation about a topic that I was interested in. So, I joined up. Now I'm seeing Reddit in the news, in magazines, and it's on the lips of a LOT of people. What I'd like to know is HOW BIG is reddit, really?