What is Preamble?

Preamble definition and meaning on Dictionary terms:
an introductory statement; preface; introduction.
the introductory part of a statute, deed, or the like, stating the reasons and intent of what follows.
a preliminary or introductory fact or circumstance: His childhood in the slums was a preamble to a life of crime.
(initial capital letter) the introductory statement of the U.S. Constitution, setting forth the general principles of American government and beginning with the words,