We document only what is not self-explanatory. We describe the mainstream use cases, handled in the most common ways. For more information see PackagedScripts or the source code. Then you can experiment.
Implementation is mostly documented by source comments. Detailed descriptions of Selenese commands are in reference files. You can find them
Selenium and SeLite GUI, some of their documentation and all their source, are accessible via special Firefox URLs that start with chrome://. (Those addresses don’t work in other browsers).
Documentation presents such URLs as text in italics, but not as links. (That’s because Firefox doesn’t allow linking to them from the internet, neither from file:// based URLs.)
If you read Object Diagrams, see also DocumentationStandard > Textual object diagrams.