Important:
"PATH is an environmental variable in Linux and other Unix-like operating systems that tells the shell which directories to search for executable files (i.e., ready-to-run programs) in response to commands issued by a user."
http://www.linfo.org/path_env_var.html
A list of the environment variables can be got by typing:" env" or "printenv" in the terminal.
Use the export command to change the environment variables.
