The .NET Framework is a library of classes, interfaces, and types that add extra power to Visual Studio .NET. These features go beyond what is normally provided by a programming language such as Visual Basic.
The .NET Framework is truly enormous. To make it more manageable, Microsoft has broken it into namespaces. The namespaces form a hierarchical catalog that groups related classes and functions in a meaningful way.
For example, the System namespace contains basic classes and methods that an application can use to perform common tasks. The System.Drawing namespace is the part of the System namespace that holds graphical tools. The System.Drawing.Design, System.Drawing.Drawing2D, System.Drawing.Imaging, System.Drawing.Printing, and System.Drawing.Text namespaces further subdivide System.Drawing into finer groupings.
Many of the .NET Framework namespaces are essential for day-to-day programming. For example, many Visual Basic applications need to produce printouts, so they use the System.Drawing.Printing namespace. Different applications draw graphics or images on the screen, so they need to use other System.Drawing namespaces.
Because so much of the .NET Framework is used in everyday programming tasks, this book doesn't strongly differentiate between Visual Basic and .NET Framework functionality. Presumably, the book could have focused solely on the Visual Basic language and ignored the .NET Framework, but it would have been a much less useful book.