A module, at the most basic level, is a collection of functions and structures.

Main Modules

Modules who have the name */main (no matter what comes before it, so addint/main as well as just main both qualify) are main modules. This means they can be executed if you add a main function to them.

If you’re familiar with other programming languages, it’s like having a main module in golang or (roughly) a .cpp file with a main method in C++ (or .c in C).

Libraries

Libraries are disbributed in the foramt of a <library-name>.chimod file, including the standard library. The standard library (which is in active development), is under the std/ directory in the src tree of your workspace.