What is "Conversation"?

[Richard Shane, Ph.D.]

Entourage 2004 v. 11.2.5
OS 10.4.8

Hi,

When emails come in, in addition to a subject line, there is a line called
³Conversation.² This always seems to have the same contents as ³Subject.²
What is ³Conversation²?

Thank you for your knowledge.

Richard