A buffer is Emacs’s working view of one piece of information. A buffer might contain a file you are editing, an Info manual, a directory listing, a Web page, a mail search, a shell session, or a temporary Help result. Some buffers are connected to files; many useful application buffers are not.
The mode line identifies the selected buffer and its major mode. Press C-e m whenever you want to hear it. Common buffer commands include:
Switch to another buffer by name. Completion lets you narrow the choices instead of remembering the complete name.
Open a buffer list. In that list, use C-h m to learn its navigation, selection, saving, and cleanup commands.
Close a buffer that you no longer need. Emacs asks before discarding unsaved file changes.
Moving to another buffer changes the selected work object without closing the one you left. This makes it practical to keep a document, its reference material, a shell, and related application results available together.