Here's the difference:

* Constellations: Officially recognized groupings of stars that form a specific pattern in the sky. They are defined by the International Astronomical Union (IAU) and are often based on ancient myths and legends. Examples: Ursa Major (Great Bear), Orion.

* Asterisms: Patterns of stars that are not formally recognized as constellations but are easily recognizable. They can be a part of a constellation or include stars from multiple constellations. Examples: The Big Dipper (part of Ursa Major), the Summer Triangle (made up of stars from three different constellations).

So, while an asterism is a pattern of stars, it doesn't have the official designation of a constellation.