Explore the concept of ergodicity and its breaking in quantum systems through the lens of quantum entanglement in this comprehensive lecture. Delve into the motivation behind studying this phenomenon and examine various types of experiments used to investigate it. Learn about simple and concrete models, including onsite disorder and quantum quench experiments. Investigate the role of symmetry breaking and the three key ingredients involved in these processes. Gain insights into thermalization, statistical mechanics, and global conservation laws. Analyze the concepts of prethermalization and weak ergodicity breaking. Examine the interplay between entanglement, complexity, and thermalization, concluding with a discussion on the Eigenstate Thermalization Hypothesis (ETH).