A database is a structured system that stores data in a way that facilitates easy access, management, and updating. Databases use various models, such as relational, NoSQL, or hierarchical, to organize data into tables, documents, or other structures. Relational databases, for example, use tables with rows and columns, and support SQL (Structured Query Language) for querying and manipulating data. NoSQL databases, on the other hand, are designed for handling unstructured or semi-structured data and offer flexible schema designs. Databases are essential for applications ranging from enterprise systems to web applications, enabling users to efficiently manage large volumes of data and perform complex queries.