Variables can be set while in the shell, or placed in the shell resource file .cshrc which is executed at login time. Please read the man pages man csh for a more complete discription of the use of set and the variables that can be set. If you are using a different shell you must read the appropriate man pages for that shell. Also, following is a few more useful csh set usages. The setenv command is followed by the name of the environment variable to be set, then the value to set the variable to.
Many software packages use environment variables to specify pathnames.
You can also use man setenv for help as well. Displays the value of a shell environment variable. You can either use printenv by itself, which will display all variables and their values for you. Or, you can use printenv followed by an environment variable name, in which case the value of that particular variable will be displayed. Define a string to be equivalent to a shell command.