Well known Masonic symbol, but by no means exclusive to Freemasonry. It can appear in a triangle, a star, a cloud, on its own. It usually refers to the notion of ‘something higher’ whatever that is for a specific lodge or Freemason.
All-Seeing Eye,
whom the Sun. Moon, and Stars obey, and under whose watchful care even Comets perform their stupendous revolutions, pervades the inmost recesses of the human heart, and will reward us according to our merits.
Ahiman Rezon. Rituals of Freemasonry by Daniel Sickels (1870)
The eye can look to the left, right or straight ahead. I know of no specific meaning to that detail.
Top: Duncan’s Masonic Ritual and Monitor (1866) by Malcolm C. Duncan
Bottom, both: general images found online.