This great program/tutorial will introduce you with the heart of Pattern Recognition, unsupervised learning of Neural network called k-means clustering. When User click picture box to input new data (X,Y), the program will make group/cluster the data by minimizing the sum of squares of distances between data and the corresponding cluster centroids. Very well documentation. Different color code represent the clusters.
This algorithm is a standard and popular algorithm for unsupervised learning of Neural network, Pattern recognitions, Classification analysis, clustering analysis etc.