Cmd, or command prompt, is the shell of the Windows Operating system. It is here where you can tell your computer to execute commands in the simplest way possible; text commands. There's no fancy user interface to tell it what to do. Just a black screen with white text.
To run cmd on Windows 7 type "cmd" into the search box and hit enter. It will run automatically. On earlier versions of windows you will have to use Run and then type cmd+enter. You will be greeted with C:/Users/user: | This is where you can tell cmd what actions you want done. If you are not happy with the color setup you can type COLOR (Numbers 1-100 or letters) to change the color. Color 3 and Color a are both greens. Color A than color 3.
Once you have your color scheme arranged it is time to tell it to start doing commands. You could start off simple by finding out your IP address with Ipconfig. Another useful command is Tracert followed by an IP address or a URL. This will show how many hops (steps) it takes to reach a destination on the web from your current location. This will count for a maximum of 30 hops unless you type -h (number) after the tracert commands. This will tell cmd exactly how many hops you want to set as a maximum. -w (number) will tell it how long to wait before it considers the connection "time out" or lost. If you have a slow connection speed this will be your best bet.
The next and most widely used command on cmd is Ping. By default Ping sends a request for 32 bytes of data to a server and waits for it to send the 32 bytes back. It will do this a default of 4 times before telling you your highest, average, and lowest connection speed in milliseconds. This is a good tool for testing internet connection speed against a server or to see if an internet connection problem originated from your connection or your website. Another (illegal) use for this is attacking a website with massive ping requests in an attempt to slow it down. This can be done using the commands -t (makes the ping process go until it is interrupted) and -l (number of bytes after -l). The higher the number of bytes the higher amount of work the server has to do. There is a cap of 64,000 bytes, but most computers can't handle that with the default timeout time. Once again, typing -w (time) will allow you to reset that amount.
The last commands are Cls and Title. CLS just clears the cmd screen from all previous text. Title (followed by text) is what the name of the cmd window will be. So for instance if you wrote Title The legionnaire's den. the title of the cmd window would change from cmd.exe to "The Legionnaire's Den.".