Emacs is a free text editor which can be used as an ASCII-oriented interface to Macaulay2. The best way to edit Macaulay2 code or to run Macaulay2 is with Emacs or its MacOS variant Aquamacs. Emacs is available as part of many operating systems, as well as from https://www.gnu.org/software/emacs/.
The source of this document is in Macaulay2Doc/ov_editors_emacs.m2:459:0.