Command Prompt is fun to use when you know the commands.Whenever you type a command cmd first looks it up in its own directory to check if it is an internal command then it goes to the external commands directory.
For going to external commands directory it needs to know where the programs’ file are kept.
The PATH variable gives it the information about the various directories where to look for the commands.
So when you install a new program either its path is set automatically during setup or has to be done manually.
Setting Path is done manually by the steps shown below:
I made this during answering the question at some other place.Like if you find this useful.