Business Intelligence Development Studio or BIDS is a Visual Studio based application used to develop SSIS, SSAS or SSRS solutions. It was introduced with the release of SQL Server 2005 and is also available in the 2008 and 2008 R2 releases of SQL Server.
It is not the same as Visual Studio. It only contains the BI related project types and designer extensions. The 2005 version is based on the Visual Studio 2005 shell, where the 2008 and 2008 R2 versions are based on Visual Studio 2008 shell. Thus the development remains in the familiar VisualStudio environment, but is focused on developing Business Intelligence solutions.