This is the back of a CPU. This is where you'll plug up your monitor, mouse, keyboard, speakers, etc.
You have 2 fans in the back so it'll keep your CPU from overheating.
There's also an on off switch in the back to completely shut everything down.
This is the front of the CPU. This is where you insert your DVD/CD's, insert your floppy disk, it's also where the reset, eject, and power buttons are.