Also known as the ‘ Eye of Providence’ , or the all-seeing eye of God, the symbol itself is often shown in pictures as an eye surrounded by rays of light or a ‘glory’ and usually enclosed by a triangle. It represents God's omniscience and omnipresence
In Medieval and Renaissance European iconography, the Eye of Providence often incorporated the triangle which was an explicit image of the Christian Trinity of God the Father, Jesus Christ His Son, and the Holy Spirit.
The same ‘eye of god’ is found in Egyptian mythology as the Eye of Horus. The symbol also appears in Buddhism, where Buddha is referred to as the "Eye of the World".
Eyes are also painted on boats to protect the superstitious fishermen from the 'Evil Eye' - a curse invoked by the sin of envy, which can initiate a spate of bad fortune.
In conclusion, the All-Seeing Eye symbolises the eye of God, keeping watch on mankind.