What is a Virtual Machine?

I have recently started trying to learn Visual Basic and I came across the .NET Framework (I've heard it lots of times before though). The definitions I have found state that a framework is like a skeleton on which programs are run on (which still confuses me), and that a framework is something like a Virtual Machine, independent on the OS.

I feel like I should be able to grasp what a framework is before I move on with my studies/trials, so I came here for some clarity.
Can someone explain like, what a Virtual Machine is, without requiring some special background knowledge?

Thanks in advance.

A virtual machine is basically an operating system that's installed on a program within your main operating system.

Your Main OS(Windows/Mac/Linux) --> VirtualVM --> Another OS

Its basically a program that runs operating systems on your main OS

Example: Your OS -> Virtual machine -> Another OS (Mac,Windows,Linux)

None of these answers are correct.
In terms of programming and .net specifically, a virtual machine, in short runs and manages your code.
The .NET virtual machine is called the CLR, Common Language Runtime. Like many other VMs including the closely rated JVM (Java Virtual Machine), it JIT compiles your .NET program which is just high level IL to actual native code. It also manages your memory and most of your resources for you in a process called garbage collection. This is why you don't hVe to worry about allocating and freeing memory in .net languages. On top of all that it provides a foriegn function interface to allow your program to interface with c and c++ code. Most things done in .net languages are backed by c code that do the actual process like interacting with the os and its resources. The exe file that represents your program is merely a CLR bootstrapper (starter) that feeds your program, which is IL stored in the data region, to the CLR.
With out the CLR your code and program are literally useless because nothing is there to run it.