In k-means,the centroid of each cluster is used as a representative of the cluster center.
The procedure has four steps: (1) the k of the items from the data set is selected as the representative centroid; (2) all of the items are assigned to the centroid cluster; (3) the centroid is calculated based on the new cluster; (4) if all the items still belong to the original cluster, it ends, otherwise step (2) is repeated