$PATH

From Fluxbox-wiki

In a unix like operating system when smoeone says $PATH this is an enviroment variable that contains all the paths that your shell will look to execute a program. To find out what your $PATH is simply open a terminal and type

 echo $PATH

You might see something like

 » echo $PATH
 /bin:/usr/bin:/opt/bin:/usr/local/bin

It can be much longer. To append to your $PATH for tempoary time simply type

 export $PATH=$PATH:/usr/local/games/bin

And this will add /usr/local/games/bin to your $PATH variable. For a more permanent solution you should add this to your shellrc file. For BASH users this will be ~/.bashrc and ZSH users should use ~/.zshrc or something similar. You might even also consider adding things like this to ~/.profile