I am assuming you are logging into some university computing clusters. At my university, we have a system that uses the module command to load different programs as you are describing.

Basically, the module command modifies your environment so that the path and other variables are set so that you can use a program such as gcc, matlab, or mathematica. To see some of the changes, run env to see your environment variables, then run module load matlab or some other available package, and then run env again to see the updated variables.

I'm not sure of the details, but you can try

module help

or visit http://www.tacc.utexas.edu/tacc-projects/lmod for more information