Here's a brief explanation of the different Visual Basics:
- Visual Basic 6 (VB6, or classic VB)
- Released around 1998, this was the last iteration of Microsoft's original "Visual Basic." It has the beginnings of object-oriented development, but it requires the Visual Basic Runtime for applications to run. A lot of companies have used VB6 for internal business applications. It was superceded by VB.NET and the .NET Framework.
- Visual Basic for Applications (VBA)
- VBA shares the same code base as VB6 and in 1996 was available to be licensed to developers to include in their own applications. This is how VBA appears in Microsoft Office, as an embedded language that can be used to control Office's various applications. It's important to remember that VBA, which is still used to code office applications, is over a decade old and may feel as such when one is used to working with .NET.
- Visual Basic .NET (VB.NET)
- VB.NET was a radical departure from VB6. Though subsequent iterations of VB.NET have been referred to in sequence (e.g. VB7, VB8, etc.) by many developers, VB.NET shares very little with VB6 and VBA other than the BASIC syntax. Many consider it more of a new evolution in BASIC rather than an evolution in Visual Basic. Because it's entirely different from VBA and VB6, you cannot not use VB.NET code directly in VBA.
- Because VB.NET code compiles down to the same managed intermediate language code as C# and shares the same .NET APIs, you may feel more commonality between C# and VB.NET than VB6 and VB.NET from a programming perspective.
If you anticipate doing a lot of development in VBA, I would highly recommend the VBA Developer's Handbook, Second Edition, by Getz and Gilbert.
Learning the VBA syntax for Word will certainly help you when you go to use Excel, Access, etc. However, each application has its own API that provides a set of objects and methods unique to its domain. For example, I'm very familiar with programming in VBA in Excel and Access, but I have never done macro programming in Word. Although the code syntax would be the same, I'd have to learn Word's API to be able to program against it.
The nice thing about some of the Office applications (Excel, for example) is that you can record a macro, see what code it generates, and then tweak that code to do what you want. That's largely how I got started in programming.