Lmod is a Lua based module system. Modules allow for dynamic modification of a user's environment under Unix systems. See www.tacc.utexas.edu/tacc-projects/lmod for a complete description. Lmod is a new implementation that easily handles the MODULEPATH Hierarchical problem. It is drop-in replacement for TCL/C modules and reads TCL modulefiles directly.
lmod is a re-implementation and extension of the popular "modules" system for maintaining software environments. It is a considerable improvement, and you should have no hesitation in using this over the original modules software. If you ever install more than one version of some software on your computer, you need this package.
This is a tremendous advance in managing computing cluster infrastructure. Kudos to Robert McClay for advancing the state of environment modules.