The front of your computer has lights, buttons, ports, and drive doors. Many different combinations and looks are out there. You cannot access your hard drive from outside, but there is a light that shows when it is busy. Your CD or DVD drive has a button to open the disc tray or a slot to feed in a disc. The Power button is usually on the front but might be somewhere else. A Reset button does a warm boot, but not all cases have one. There are also usually at least two USB ports and two or more sound ports, and maybe a FireWire port on the front.
It is important not to shut the computer down with the Power button or restart with the Reset button unless the computer is truly stuck in a loop and won't shut down with software commands.
The back of the computer is where you usually attach external devices that will remain connected all the time, like your monitor, keyboard, mouse, and printer. There is a standard color-coding scheme as well as different shapes for differnt kinds of connections. Not all computers use the standard colors. The mouse and keyboard ports are PS/2 ports. Never connect or disconnect a device from a PS/2 port while the computer is on. You can kill the port or even the motherboard. USB devices can be plugged in and unplugged while the computer is on, but you need to use the Safely Remove Hardware feature or the computer may ignore the port until you reboot the computer. Also, removing a device while the computer is trying to write to it can damage files.
To look inside the computer you must take off part of the case. Some cases have 2 or 3 screws that keep the case on. Other cases just slide back and off. Devices that must attach to the motherboard inside the case include the power supply, RAM, hard drive, CD/DVD drive, other media drives, plus the lights, buttons and ports on the case. Some of the ports that show on the back of the computer connect directly to the motherboard, especially mouse, keyboard, and video. Others are part of a peripheral card that plugs into a slot on the motherboard. Be sure to ground yourself by touching a metal part of the case before touching anything inside it. Sparks kill computers.
You need protection against different kinds of electrical problems: fried parts, accelerated aging, and lost data. These are caused by the electricty coming in from the wall not being constant. A power surge sends a huge blast of power in microseconds. Variations up and down that are not immediate disasters still cause the parts to wear out sooner. A sudden power loss can corrupt whatever file was being written at the moment. An Uninterruptible Power Source (UPS) can handle all of these problems by blocking surges, conditioning the power, and supplying battery power when the electricity goes out.