Flickr: Creative Commons

So this Creative Commons thing is just like a copyright law but without the lengthy legal process involved...? Alright I can dig that. The symbols seemed a bit confusing at first but the key on the side of the page certainly helps out.
 This guy says its alright to use other people's images as long as you give them credit.
 This one says the same as above but you can't use 'em for commercial images.
 So this means you can borrow and use the image but you can't change it, ever.
 Alright this one talks about licenses and things so now I'm slightly confused. So people can use your work as long as they utilize a license similar to yours.
Now the combinations of these symbols is a bit over my head.

Photo by ucumari