A technique for communicating a remote server in order to retrieve or send information with no need of complete pages refresh.
For beginners or advanced users/developers. Sites help and/or give in detail, guides that describe how to create or modify things, these shouldn't describe the core language, as that is already covered by the category named "Reference."
Personal pages whose main content is about the language.
Standardized, commonly accepted or adopted code styles, naming conventions and good practices such the good use of the global namespace and the like.
Tools for developers: testing libraries and utilities, performance, debuggers, automated tests, linters, toolkits and code editors.