A decision tree is a graph of decisions and their possible consequences, (including resource costs and risks) used to create a plan to reach a goal. Decision trees are constructed in order to help with making decisions. A decision tree is a special form of tree structure. Decision tree has two other names: Regression trees approximate real-valued functions instead of being used for classification tasks. (e.g., estimate the price of a house or a patient’s length of stay in a hospital) and Classification tree, if the Y is a categorical variable such as: sex (male or female), the result of a game (lose or win).