You're likely referring to the Summer Triangle, a prominent asterism (a recognizable pattern of stars) visible in the Northern Hemisphere during the summer months.

The three stars that make up the Summer Triangle are:

* Vega (in the constellation Lyra, the Lyre)

* Deneb (in the constellation Cygnus, the Swan)

* Altair (in the constellation Aquila, the Eagle)

These stars are all very bright and easily visible, making the Summer Triangle a great starting point for stargazing.