The module system is a program, running on most supercomputers, that simplifies using different software in a precise and controlled manner. Oftentimes a supercomputer has more software installed than the average user will ever use. Frequently there are also multiple version of the same program available at the same time, to enable backward compatibility. A prominent example of this are Compilers, which sometimes have the tendency to break older programs with new versions.
To get a list of all currently loaded modules, one can employ
$ module list
and might receive something like:
Currently Loaded Modulefiles: 1) DEVELOP 3) intelmpi/2017.4 2) intel/16.0 4) likwid/system-default
$ module avail
lists all available (loadable) modules and module groups. With the information of these two commands, one can select module to load/unload/switch with
$ module load/unload x
to load or unload module x or
$ module switch x y
to switch out module x for module y. This is especially useful, to switch to a different version of the same program
Since a lot of applications rely on 3rd party software, there is a program on most supercomputers, called the Module system. With this system, other software, like compilers or special math libraries, are easily loadable and usable. Depending on the institution, different modules might be available, but there are usually common ones like the Intel or GCC Compilers.
If you recurrently need lots of modules, this loading can be automated with an sh-file, so that you just have to execute the file once and it loads all modules, you need.