B

body

The principal content of a message, typically displayed to each recipient as an immediate result of opening the message.

body part

Any part of a message following the headers and holding content. A simple Internet message, or RFC 822 message, has just one body part, namely the body. Body parts in a MIME message can be of widely different types, for example plain text, rich text, image, audio, or video. A body part can itself contain subparts.