Re-open *scratch* buffer in Emacs?

GNU Emacs default bindings:

C-xb *scratch* RET

or, more verbosely

M-x switch-to-buffer *scratch* RET

The *scratch* buffer is the buffer selected upon startup, and has the major mode Lisp Interaction. Note: the mode for the *scratch* buffer is controlled by the variable initial-major-mode.

In general you can create as many “scratch” buffers as you want, and name them however you choose.

C-xb NAME RET

switches to a buffer NAME, creating it if it doesn’t exist. A new buffer is not associated with a file on disk until you use C-xC-w (or M-x write-file RET) to choose a file where it should be saved.

M-x text-mode RET

changes the current buffer’s major mode to Text mode. To find all the modes available (that is, without requiring any new packages), you can get a list by typing:

M-x apropos-command -mode$ RET