"Clustering is the process of grouping data objects into a set of disjoint classes, called clusters, so that objects within a cluster have high
similarity to each other, while objects in other clusters are more dissimilar. Clustering is an example of unsupervised classification.
""Classification"" refers to a procedure that assigns data objects to a set of predefined classes. ""Unsupervised"" means that clustering does not rely on predefined classes and training examples while classifying the data objects."