In astronomy, a star cluster is a group of stars that are gravitationally bound and typically formed from the same molecular cloud. They can be open clusters (loosely bound and containing fewer stars) or globular clusters (tightly bound and containing many stars).In computing, a cluster is a set of loosely or tightly connected computers that work together so that they can be viewed as a single system. Clusters are used for high availability, load balancing, and parallel processing.This refers to a geographical concentration of interconnected businesses, suppliers, and associated institutions in a particular field. An example would be Silicon Valley, which is a cluster of technology companies.