If a program opens multiple windows, does each window use a core?

[ByronX]

So lets say Im running android emulators. I open multiple emulators at once, with the same program(Nox). Does each emulator use one core or do they all share one core?

 

[gamerk316]

Each thread will rotate between cores as determined by the Windows scheduler.

 

[ByronX]

MERGED QUESTION
Question from ByronX : "Does multiple cores help with multiple emulators when using Nox Player?"

I plan on running multiple nox emulators all at the same time. I want to know if it'll run faster with more cores. Thanks


Tdlr: should I buy an intel core i3 with dual core or a intel core i5 with quad core.