The Eye of Providence symbolizes the all-seeing eye of God. It shows an eye often surrounded by rays of light. This symbol is found on a lot of coats of arms, seals, and logos of states and countries.
The Eye of Providence is also part of The Great Seal of the United States, which appears on the one-dollar bill. There it is shown above a pyramid of 13 steps, that stand for the original 13 colonies. It also appears on the Gravity Falls series, discussed by the character, Bill Cipher.
The symbol is explained by the motto that appears above it. “Annuit Coeptis” means, “He [God] approves (or has approved) [our] undertakings.”