Hi
Eisasuarez
your question prompted me to register so that I can reply.
I'm not sure what your experience and levels are (I can't provide a diagram) but I'll do my best to explain what .net is.
Microsoft was gaining enormous popularity in the business market in the 90s. They had VBA for Excel and Access, then Word and Powerpoint even, they had compilers for C++ (Visual C++) and the very popular VB. VB got very mature with Version 6. At around that time, the Web was getting more and more important for business, and they had a clunky old technology called ASP (Active Server Pages) This used VBScript at the back and sent back html to the requesting browser.
Microosft worked for hard between about 1998 and 2001 to create a brand new technology/suite of tools to compete viably in the coming internet age. So gone were VB6, VBA (both of whch used an object technology protocol called COM), C++, vbscript and various other tools. An in came .Net. The most key thing to know about .net is that it's fully object-oriented, allowing for encapsulation, polymorphism and inheritance, the holy OO trinity.
.Net is mainly 3 things.
1) a compiler (the Common Language Runtime or CLR)- this is like a mini-operating system that can run .net programs you write.
2) a language that can target this compiler, here there were many but the two main ones were C# and VB.net
3) the vast underlying libraries that were written to be compatible with the .net Compiler or CLR
let's look at each of these
the Compiler or CLR is really a Microsoft version (rewrite) of something like the java runtime. A piece of software that loads the .net program you've written that in whatever language that will call on the underlying .net libraries. You can't do anything without this. You can't run an Excel VBA macro without Excel so in a sense Excel is the compiler and run-time of an Excel VBA program.
The language became much less important in one sense because any language that conformed to the spec could target the CLR and the libraries.
The libraries are key, in there you have things like string, double, bool, ArrayList, and quite literally across about 30+ dlls thousands of other classes.
very famous .net libraries do specialised things like
access data from robust back-end database servers like SQL Server, DB2, Ingres, MySQL or Oracle (ADO.net) but getting replaced with LINQ and Entity Framework
ASP.net ...a heavily souped up version of the 90s ASP - a web framework for writing web apps - this is slowly getting replaced with ASP.net MVC (model view controller)
Winforms - writing windows apps - also debatable whether it's getting replaced but if it is it's stuff like WPF or Silverlight a much more complicated version of Winforms with more capabilities but much harder to learn
Cryptography
Regular expressions
etc..etc..
There are many .net libraries.
in conclusion, .net is a platform for running the .net programs you've written in a .net language and that consume the contents of underlying .net libraries that contain primitive (but highly useful functionality like strings and integers) and other libraries that help you build GUIs (Web or Windows) and target services or Write internet applications that run on a server but appear on a client's browser.
.net Was built to allow for a convergence of technologies using the Object-Oriented paradigm but in a much more complete and thorough way than had existed in COM or VB6/VBA. The idea was that you could write a .Net program (that targets .net libraries) in a language of your choice and you could use robust industrial strength object orientation to express your business solution/design.
I hope this helps.
P.S: VBA has not gone. but it has been deprecated as a standalone environment (the way VB6 was) and can now only automate office apps. it just seems as if MS cannot (or are not even trying) to kill VBA. We shall see.