What is "asterism" in observational astronomy?

In observational astronomy, an asterism is a pattern or group of stars that can be seen in the night sky. Asterisms range from simple shapes of just a few stars to more complex collections of many stars covering large portions of the sky. The stars themselves may be bright naked-eye objects or fainter, even telescopic, but they are generally all of the similar brightness to each other. The larger brighter asterisms are useful for people who are familiarizing themselves with the night sky.

The "Orion's Belt" is an asterism of three stars that appear about midway in the constellation "Orion the Hunter". In this case, asterism is so-called because it appears to form a belt in the hunter's outfit. It is one of the most famous asterisms used by amateur astronomers. Asterisms do not have officially determined boundaries and are a more general concept that may refer to any identified pattern of stars.