M&M's (styled as m&m's) are "colorful button-shaped
chocolates" produced by Mars, Incorporated and similar to and inspired by Smarties. The candy shell, each of which has
the letter "m" printed in lower case on one side, surrounds
a filling which varies depending upon the variety of M&M's.
The original candy had a milk chocolate filling which, upon
introducing other variations, was branded as the "plain"
variety. "Peanut" M&M's, which feature a peanut coated
in milk chocolate, and finally a candy shell, were the first
variation to be introduced, and they remain a regular variety.
Numerous other variations have been introduced, some of
which are regular widespread varieties (such as "peanut
butter", "almond", "pretzel", "crispy", and "dark chocolate"),
while others are limited in duration or geographic availability. The MMM Family video.