This specification defines HyperText Markup Language as implemented in the broader diversity of web browsers, including Rhapsode, Lynx, Dillo, Netsurf, Weasyprint, etc. HTML is a language for annotating plain text with its semantic structure, and to reference related resources. HTML specifically does not dictate how its text should be presented. For the sake of rendering to a variety of devices, and to ease website authoring & maintenance.
HTMLite is meant to be loosely compatible with WHATWG's HTML specification whilst being tractible to understand and implement. Reflecting what's supported/used by most browser engines and web pages, rather than the popular few.
HTMLite is an application of XMLite, and is based fundamentally on XMLite-Model. It also defines the HTML syntax as an alternative to XMLite-Syntax.