Which describes an operating system this is multitasking

Okay, a Multitasking Operating System (OS) allows you to run many processes (or tasks) "simultaneously".

They do not actually run at the same time, of course, since there is only one CPU.

They have to take turns working but they do it really fast (:

Also, if your CPU has multiple cores then you can, run one task on one core, and another on the other core, depending of course on how many cores you CPU has e. g. Quad-Core, Dual-Core, Eight-Core.