for questions about Emacs Lisp as a Lisp dialect, that is, questions *about the language* itself. DO NOT USE it for questions about customization or how to write an application. Emacs Lisp is the scripting and programming language that the Emacs editor is built on.
Emacs Lisp is a dialect of the Lisp programming language used as a scripting language by Emacs. It is used for implementing most of the editing functionality built into Emacs, the remainder being written in C (as is the Lisp interpreter itself).
The most common way to customize Emacs is by Emacs Lisp expressions in your init file,
Emacs packages are also predominantly written in Emacs Lisp. See A guide to learning Emacs Lisp for non-programmers for reference. The Emacs Lisp Reference is also viewable in Emacs with C-him
Use elisp for questions about the language itself, in particular, its relation to other Lisp dialects and differences from them. And when available and appropriate, use more specific tags, such as