Machine learning, a branch of artificial intelligence is about the construction and study of systems that can learn from data. It focuses on prediction, based on known properties learned from the training data. Data mining focuses on the discovery of unknown properties on the data. The machine learning also employs data mining methods as unsupervised learning or as a preprocessing step to improve learner accuracy. The performance of machine learning algorithm is usually evaluated with respect to the ability to reproduce known knowledge, while in Knowledge Discovery and Data mining (KDD) the key task is the discovery of previously unknown knowledge.