What does the little pyramid with the eye mean that's on the US dollar bill?

Question

I've seen National Treasure and everything, I was just wondering what the REAL explanation for adding it to the bill is.

Answer 1

It is a Masonic Symbol that God watches over us and the incomplete pyramid means that the work that needs to be done will never truly be finished

Answer 2

In 1782 the Eye of Providence was adopted as part of the symbolism on the reverse side of the Great Seal of the United States. The Eye, however, was first suggested as an element of the Great Seal by the first of three design committees in 1776

Answer 3

It is the Eye of Truth. No clue what it means though =p