Our build system allows the compilation and installation of simple and complex pieces of software. The description of the software bing built involves packages, modules and products.
A software package or shortly package is the largest hierarchical unit of the description of the software that should be built. The complete description of a software packages consists of all the programs, libraries, documents that should be built and copied to the target system in order to install the software. This description also accounts for extra steps that should be taken to integrate the software to its host environment, like triggering scripts indexing documentation and similar steps.
Other common names for software package are project or solution. The name software package or package is also used by the GNU Autotools, it should not be confused with packages used by package management software such as pkg on FreeBSD or apt on Debian.
A module is the smallest hierarchical unit of the description of the software that should be built, it sits just above files in that hierarchy. Typical examples of modules consists of a C program together with its manual pages, an OCaml library with its ocamldoc generated documentation, a LaTeX class, or package documentation.
It is worth to note that a simple software package may consist of a single module. Also, each module can provide its own documentation products but the software package as a whole may contain extra modules producing documentation artifacts whose scope is not limited to a specific module but may embrace several of them—typically the full software package.
Software modules can depend on external programs, packages and libraries. They also can depend on other modules found within the sofware package being built.
The products of a module are file system artifacts, like a single file or a subtree of the file system. These products are the actual artifacts representing the software package in the host system. The installation procedure of the software package usually copies products at appropriate places of the file-system but it may require to execute additional actions, like the execution of scripts.