Expiramenting With Photoshop

Today, I used Adobe Photoshop for the first time. My first impression when I saw the User Interface was that it reminded me a lot of Illustrator. It had a similar layout in terms of tool-bars and menus. I was confused at first, and had a hard time getting started. Most of the tools I tried to use responded with error messages, mentioning something about ''layers." Apparently, these "layers" are what Photoshop is all about, but I still don't get it. One tool I did know how to use was the Pen Tool. This one was simple: Just hold down the left mouse button and draw. I hope we star on some tutorials soon, so I can begin to understand this program.