A lot of people will point to it and say its Masonic imagery which isnt wrong so to speak but those like the eye are Christian symbols associated with Divine Providence. The pyrimid is 13 levels high for the 13 colonies and the unfinished part symbolizes the future potential/growth for the US.

The Great Seal was first designed in 1782 during the Continental Congress

So the Latin for Annuit Coeptis translates to "He favors our undertakings" or "Providence favors our undertakings," which historically we refers to the divine approval of the American cause (think manifest destiny). The second part Novus Ordo Seclorum " a new order of the ages" which makes since given this was a revolution and a huge new way of government.