Faust: Try this link to wikipedia. It has a picture of a pedal with SPD on one side, and regular flat pedal on the other. I clicked a few of the links from this page, and they're pretty good, too. (I like pictures!)

http://en.wikipedia.org/wiki/Bicycle_pedal

I just switched my bike from flat pedals (the kind my bike came with) to Speedplay Frogs. http://www.speedplay.com/index.cfm?fuseaction=home.frog

The Frog pedals attach to a metal cleat on the bottom of my biking shoes. They are supposed to be very easy for a beginner to learn and gentle on the knees because they have a lot of "float" (your foot can wiggle a good bit before it unhooks the cleat, so it doesn't strain your knee by forcing the knee to wiggle instead of the foot).

If you don't want to get into pedals with cleats yet, you could put toe clips/toe cages on your current flat pedals. I would take the strap off and just play with the clip part. I had toe cages on my flat pedals and it seems like they helped me learn the Frogs.