http://msdn.microsoft.com/en-us/library/ms173767.aspx
Business Intelligence Development Studio is Microsoft Visual Studio 2008 with additional project types that are specific to SQL Server business intelligence. Business Intelligence Development Studio is the primary environment that you will use to develop business solutions that include Analysis Services, Integration Services, and Reporting Services projects. Each project type supplies templates for creating the objects required for business intelligence solutions, and provides a variety of designers, tools, and wizards to work with the objects.
If you already have Visual Studio installed, the new project types will be installed along with SQL Server.