The Sitecore Documentation Experience Generator is a Sitecore template architecture visualization and documentation tool from the SitecoreUML family. Leveraging the open-source APIs associated with StarUML (on which SitecoreUML is also based), SitecoreDXG provides support for generating template data model architecture diagrams and HTML documentation from any existing Sitecore instance (PaaS and non-PaaS are both supported) that has the SitecoreUML Service for Sitecore (1.3.6+) installed.
It should be noted that SitecoreDXG is an open-source, GUI-less and easily-extensible version of SitecoreUML that was specifically designed for ease of integration into CI/CD pipelines.
See the official documentation for installation, setup and use instructions, as well as other guides and explanations.