Microsoft SQL Server is a relational database management system (RDMS) developed by Microsoft. As a database server, it is a software product with the primary function of storing and retrieving data as requested by other software applications. These applications may run either on the same computer or on another computer across a network, such as the internet.
A relational database management system means two things. First, data stored inside SQL Server will be housed in a 'relational database', and second, the SQL Server is an entire 'management system', not just a database. SQL itself stands for Structured Query Language. This is the language used to manage and administer the database server.