The main function is the low level entry point to the solidity-docgen pipeline.
The input into the pipeline is one or more of the compiler's [standard JSON outputs] with at least the ast file output selection.
Users are not expected to use the low level entry point (though they can do it if it's the better option). Rather, they would normally use a higher level integration with their development environment that will read user configuration from a standard location and know how to request the compiler output JSON files. See the hardhat module as an example.
The pipeline is relatively simple and consists of two major stages:
buildSite: Searches Solidity files for documentable items (DocItem) and assigns each to an output page, also annotating items with the context in which they appear.render: Renders each output page according to the templates.
Templates use Handlebars.
There is a special template partial (i.e. a sub-template) called item (defined in the function itemPartial) that augments an item with custom properties we call accessors that make templates easier to write, defined in accessors. Most things should not be accessors but template helpers, which are more versatile, available anywhere independently of the item partial, and can be provided by the user. A helper may become an accessor if this significantly improves template syntax.