We used random forests to build a classifier in the previous recipe, but we don't exactly know how to define the parameters. In our case, we dealt with two parameters:
max_depth. They are called hyperparameters, and the performance of the classifier depends on them. It would be nice to see how the performance gets affected as we change the hyperparameters. This is where validation curves come into picture. These curves help us understand how each hyperparameter influences the training score. Basically, all other parameters are kept constant and we vary the hyperparameter of interest according to our range. We will then be able to visualize how this affects the score.