If you are using dual boot (as you say you are),
- You can set up your system to be able
to access the files from one OS on the other.
- You will not be able run programs from one OS on the other
unless you install special software to let you do that.
“Ubuntu on Windows”, obviously, will let you run Ubuntu programs on Windows.
“Wine” will let you run Windows programs on Linux.
Virtualization is a mechanism by which you can create a “virtual machine” (VM).
This would be a substantially different setup from what you have now.
One OS, called the “host”,
must be the primary OS on the real (physical) machine,
and must be running all the time.
Then one or more other OS(s) can be installed on virtual machine(s),
which run in a hypervisor program that runs on the OS on the physical machine.
So, for example, you can have Windows as your host and Ubuntu as a guest.
As long as the computer is running, you will be able to run Windows programs.
Then you can boot Ubuntu on the VM and run Linux programs there.
What I said before about being able to access the files from one OS
on the other is still pretty much true.
VirtualBox and VMware are two well-known hypervisors.