In Macaulay2, modules are implemented as
subquotient modules. Submodules and quotients of free modules are perhaps the most common and important modules, and subquotients form the smallest class of modules that naturally includes these cases.
See
Tutorial: Modules in Macaulay2 for an overview tutorial on modules.
For additional common operations and a comprehensive list of all routines in Macaulay2 which return or use modules, see
Module.