A "data lake" refers to a centralized repository that stores vast amounts of structured and unstructured data in its raw form, allowing organizations to easily access and analyze data at scale. Unlike traditional databases, data lakes can handle diverse data types, making them suitable for big data applications. They enable organizations to store data without pre-defining its structure, offering flexibility in data exploration and analysis. Data lakes support advanced analytics and machine learning initiatives, as they provide a comprehensive data foundation for deriving insights and generating valuable business intelligence.