What does the preamble to the Constitution of the United States mean?

the preamble to the constitution is: WE THE PEOPLE OF THE UNITED STATES, IN ORDER TO FORM A MORE PERFECT UNION, ESTABLISH JUSTICE, INSURE DOMESTIC TRANQUILITY, PROVIDE FOR THE COMMON DEFENSE,...

This paragraph is considered to be the work of Gouverneur Morris of Pennsylvania, who was responsible for much of the final stylistic arranging and editing of the Constitution.

The preamble of the Constitution is the explanation of what the Constitution is about and tells the main points of it.

Ordain means to order or decree. In this case they are establishing the constitution to create the US.

Constitution