VirtualApp is like Parallel Space which allows you to launch apps from within a virtual environment which is inside of another app. I'm sure you have heard of VirtualXposed. You can use xposed modules and run apps within a virtual environment without root or xposed being present on your device...
This is a tutorial that is pretty advanced and because of that, I expect you to have a grip on regular IDA (normal instructions I mean, MOV, SUB, STR, etc). Of course it is not a requirement, you could just be viewing this tutorial out of curiosity. But it would really help to know some basic...