[For the M-R E]

Emacs is primarily a text editor. Some people say it is
THE Text Editor. I share this view.

Emacs is also a great desktop environment, both for the
text console to the graphical environment. File Manager,
FTP, ldap, mail, news clients, and anything one can imagine,
both locally and remotely.

Emacs is also a partially or fully integrated Development
Environment. For Lisp in the first instance, but any other
programming language has a place, and indeed many of these
languages have powerful extensions designed for Emacs.

Emacs is definitely what you want, a programmable text editor,
stable and mutant at a time, based on a programmable programming
language. It is a concept, the quintessence of "Free Software"
idea.

Emacs has a long history. Over the centuries it has survived
several languages and, above all, more than one operating
system and hardware platform.

Efficiency: C

When the GNU project launched its strategic alliance between
C and Lisp in the interests of free software, decided to
create an Emacs right for Unix Systems: GNU Emacs. For reasons
of efficiency related with the hardware of the era and Unix
workstations to could choose, it was decided to create a base
of primitive C functions. These functions are largely a type
of object declared Lisp_Object as a kind of C wrapper within
which the concept has become "Lispy" once again.

Depth and adaptability: Lisp

But the mass of the core functionality of the program and all
extensions that are written for it are made in a dialect of Lisp
called Emacs Lisp.