A cluster is a group of things or people with many similarities which are put together. When you are with your friend at a party, standing together around the snack table, talking and trying to gather the courage to start dancing, the two of you have formed a cluster. You are a smaller group with similar things in mind, have the similar mental characteristics, therefore you are a same cluster. The word cluster comes from the Old English words Clyster, and it means bunch. The word cluster can be used either as a noun or as a verb. For example, when using it as a noun you would say the following: My friends and I used to stand in a cluster in front of the ice cream truck. When using it as a verb, you would say the following: We would cluster around the driver asking for ice cream.
Anything you can think of can form a cluster: human beings, animals, flowers, tables, chairs computers etc. There is a difference between computer clusters and computer grids. Computer clusters is a set of computers which are connected with each other, so that they can work together as one system. They are set up to perform the same task which is controlled by software.