The Modules system manages a user's shell environment. Modules can be "loaded" and "unloaded" in a clean fashion. Loading a module typically alters or sets shell environment variables such as PATH, LD_LIBRARY_PATH, etc.
Useful module commands include:
module avail # lists available modules module list # lists currently loaded modules module help moduleName # help on the module module display moduleName # displays changes that are made to # the environment by loading the module module load moduleName # loads the module module unload moduleName # unloads the module and removes all # changes that it made in the environment module purge # unloads all modules