This is a library for regression analysis of data. That is, it attempts to find the line of best fit to describe a relationship within the data. It takes in a series of training observations, each consisting of features and an outcome, and finds how much each feature contributes to the outcome. This library also handles logistic regression, in which the outcomes are booleans. In this case, the regression would give you how much each feature contributes to the probability of the outcome and the prediction process would give you the probability of the outcome for a given new example.