Microsoft SQL Server Management Studio is a graphical tool for configuring, managing, and administering all components within Microsoft SQL Server.
SQL Server Management Studio is a tool included with Microsoft SQL Server 2005 and later versions for accessing, configuring, managing, administering and developing all components within Microsoft SQL Server. The tool includes both script editors and graphical tools which work with objects and features of the server.
SSMS combines the features of Enterprise Manager, Query Analyzer, and Analysis Manager, included in previous releases of SQL Server, into a single environment. In addition, SSMS works with all components of SQL Server such as Reporting Services and Integration Services. Developers get a familiar experience, and database administrators get a single comprehensive utility that combines easy-to-use graphical tools with rich scripting capabilities.
On Wikipedia: SQL Server Management Studio