visual studio and microsoft's terminology
visual studio is the Integrated Development Environment software that allows GUI creation of a project (source & resources)
The Professional editions include most of the components below, but the Express editions must each be downloaded separately and have slightly fewer features...
The "code editor" with tabs etc. is a built in...
To actually use VS you must install the component "products" (compiler & debugger for each language)
C# (MS version targeting the .NET language)
Visual Web Developer (asp.net)
Microsoft has made additional use Visual Studio by allowing it to create Report Projects for SQL Server (and hence CRM and WSS)