Machine learning is the essential component in modern AI systems for a wide range of real-world applications. In this chapter, we will start from the fundamental concepts in machine learning. First we will briefly introduce the history of AI and some successful applications achieved by machine learning and deep learning. Then we will talk about the objective function and model training, the structure of neural networks, and different categories of machine learning methods. Lastly, we will discuss the metrics used to evaluate different aspects of ML models and introduce several platforms and frameworks for machine learning research and deployment.