This document introduces machine learning and discusses why programmers need to know machine learning. It describes the difference between programming and machine learning. Machine learning is hard because it involves inducing functions from examples to generalize to new examples, rather than implementing specified functions. The document discusses real-world machine learning applications like recommendation systems. It recommends using Python and Scikit-Learn for machine learning tasks, as Scikit-Learn provides easy-to-use implementations of popular algorithms with consistent APIs and documentation.