This is the computer itself. Sometimes referred to as the harddrive, tower, or CPU.
Monitor
This is where the picture from the computer tower is displayed. Just because the monitor is turned off, that does not mean that the computer is off. Just like if you turn the TV screen off at home while a DVD movie is playing, the movie continues to play unless you turn off the DVD player or use the DVD controls to stop or pause the movie.
Keyboard
This is the imput device that allows you to type on your computer. If the keyboard was not connected to your computer or loose at the time the computer was turned on. You will have to restart your computer once it is properly connected.
Lights on the keyboard for the Num Lock, Cap Lock, and Scroll Lock keys will toggle on and off when the corresponding key is pressed on the keyboard. If these lights do not turn on and off, your keyboard is not connected for functioning properly.
Switch
A switch is used when there are limited network connections and we wish to connect more devices connect to the network than there are available connections. This devices creates many more network connections from one.
A common problem is that the main ethernet connection to the wall is unplugged or that the power to this device is off. Either of these cases will disconnect all other devices from the network.
Ethernet Cable
This cable is used to connect a device into the network. Commonly referred to as a network cable or wire, cat5, patch cord or some even refer to it as an "internet wire".
Power Strip
Many people overlook the possiblity that the power strip is turned off and therefore unable to supply electricity to anything plugged into it. It is one of the first things to check when something "won't come on".