A method that combines several models to get better results.
Ensemble Learning is like asking the whole lunch table for an answer. One kid may be way off, but the group is less silly.
You meet it in Classification. You meet it in Regression too. It makes results steadier, but it is harder to train and run.
Gradient Boosting
Gradient Boosting is a classic path inside Ensemble Learning.
Bias-Variance Tradeoff
It often mixes several models to lower variance and make results steadier.
Classification
In Classification, Ensemble Learning often uses voting to pick the final class.
Regression
In Regression, Ensemble Learning often averages several predictions.