Windows – Running Windows and macOS simultaneously on two screens

Bootcamp is designed to allow you to change your operating system while the computer boots.

Nothing allows you to swap purely back and forth between operating systems that way. What you can do is use software that runs Windows in OS X with hardware virtualization, a huge step up from the software virtual machines of old.

There are three good options: Parallels, VMWare Fusion, and VirtualBox, the last of which has the advantage of being free.

If you want more technical details, particularly the ones that drove an edit to improve this answer, read the comments below.

I use Parallels for virtualization but I also run three OS simultaneously (OSX, Windows 7 and Windows 8).

My settings are: 2 cores and 2 GB of RAM for each VM and more important VT-x support enabled, in your screenshot the first checkbox under Advanced Options.