Ensemble methods compose of a set of diverse weaker models to obtain better predictive performance. The individual models are trained separately and their predictions are then combined in some way to make the overall prediction. Ensembles, hence, contain multiple ways of modeling the data, which hopefully leads to better results. This is a very powerful class of techniques, and as such, it is very popular. This class includes boosting, bagging, AdaBoost, and random forest. The main differences among them are the type of weak learners that are to be combined and the ways in which to combine them.