Creating Buffers - GNU Emacs Lisp Reference Manual

This section describes the two primitives for creating buffers. get-buffer-create creates a buffer if it finds no existing buffer with the specified name; generate-new-buffer always creates a new buffer and gives it a unique name.

Other functions you can use to create buffers include with-output-to-temp-buffer (see Temporary Displays) and create-file-buffer (see Visiting Files). Starting a subprocess can also create a buffer (see Processes).

— Function: get-buffer-create name

This function returns a buffer named name. It returns a live buffer with that name, if one exists; otherwise, it creates a new buffer. The buffer does not become the current buffer—this function does not change which buffer is current.
If name is a buffer instead of a string, it is returned, even if it is dead. An error is signaled if name is neither a string nor a buffer.
          (get-buffer-create "foo")
               ⇒ #<buffer foo>
     
The major mode for a newly created buffer is set to Fundamental mode. (The variable default-major-mode is handled at a higher level; see Auto Major Mode.) If the name begins with a space, the buffer initially disables undo information recording (see Undo).

— Function: generate-new-buffer name

This function returns a newly created, empty buffer, but does not make it current. If there is no buffer named name, then that is the name of the new buffer. If that name is in use, this function adds suffixes of the form `<n>' to name, where n is an integer. It tries successive integers starting with 2 until it finds an available name.
An error is signaled if name is not a string.
          (generate-new-buffer "bar")
               ⇒ #<buffer bar>
          (generate-new-buffer "bar")
               ⇒ #<buffer bar<2>>
          (generate-new-buffer "bar")
               ⇒ #<buffer bar<3>>
     
The major mode for the new buffer is set to Fundamental mode. The variable default-major-mode is handled at a higher level. See Auto Major Mode.
See the related function generate-new-buffer-name in Buffer Names.

27.9 Creating Buffers