Machine learning can solve many types of tasks. Three most common types are:

1. Classification

To specify a specific one of the k categories for the input, the learning algorithm usually outputs a function
f : Rn → {1,2,...,k}
For example, image classification algorithms in computer vision solve classification tasks.

2. Regression

The program predicts the output for a given input. The learning algorithms usually output a function
f : Rn → R
Such tasks include predicting the claim amount of a policy holder to set an insurance premium or predicting the security price.

3. Clustering

Based on internal similarities, the program groups a large amount of unlabeled data into multiple classes. Same-class data is more similar than data across classes. Clustering tasks include search by image and user profiling.

Classification and regression are two major types of prediction tasks. The output of classification is discrete class values, and the output of regression is continuous values.