FileStream is a feature in Microsoft SQL Server that allows users to store and manage large binary files, such as images, videos, and documents, directly in the database. This capability enables efficient handling of unstructured data while maintaining the benefits of database management, such as security and transaction support. With FileStream, files are stored in the file system but are linked to the database, allowing for easy access and retrieval. This integration helps improve performance and simplifies backup and restore processes, as the files are treated as part of the database, ensuring data consistency and integrity.