Welcome to Roll20! Pat's links are a good place to get started (especially the crash course tutorials!), and you'll find a lot of other useful information in the Roll20 wiki too. Kristin's new Introduction to Tabletop RPGs video series (Pat's first link) might be very hand as a place to start. It does a great job of talking about the hobby, what kind of games are out there, and even advice on how to find a group to play with. There are many, many more types of games than just D&D, so it might be worth taking a look to see if that's where you want to start or if there might be a different system or setting that would be fun for you.
