GNU Emacs Lisp Reference Manual
Chapter 24: Buffers
A buffer is a Lisp object containing text to be edited. Buffers
are used to hold the contents of files that are being visited; there may
also be buffers that are not visiting files. While several buffers may
exist at one time, exactly one buffer is designated the current buffer at any time. Most editing commands act on the contents of the
current buffer. Each buffer, including the current buffer, may or may
not be displayed in any windows.