SQL Server is a relational database management system (RDBMS) developed by Microsoft. It is used to store and manage large amounts of data, and is commonly used in businesses and organizations for various purposes such as tracking sales and inventory, managing customer data, and analyzing business operations through data analysis and reporting. SQL Server supports the SQL query language and provides tools for creating, editing and managing databases. It also offers features such as data encryption, replication, and high-availability options for mission-critical applications.