Machine learning is a type of artificial intelligence that uses algorithms and data to allow computers to learn without being explicitly programmed. It works by finding patterns in large amounts of data and using what it learns from that data to make decisions or predictions. There are three main types of machine learning: supervised learning, unsupervised learning, and reinforcement learning. Machine learning has many real-world applications including traffic prediction, virtual assistants, spam filtering, and fraud detection. Some commonly used programming languages for machine learning include Python, Java, C, C++, R, and JavaScript.