In this section, we'll be exploring the concept of regression and how it applies to machine learning. The three types of regression that we're going to be covering are linear regression, decision trees, and decision forests. But regardless of the method, the purpose of any good regression model is to examine the relationship between two or more variables. And what makes regression such a powerful tool is that it gives us a mathematical process to confidently determine which factors matter most, which factors can be ignored, and how these factors might influence each other.