When they need to work on it again, they just resume it, and the virtual machine wakes up in the same state as before. This takes the current state of the machine running in the host Mac’s memory and saves it to disk (or an SSD). One of the things many Parallel users do frequently is suspend a virtual machine, rather than shutting it down, when they are no longer using it. That’s true on the Intel side for Parallels 17, though I’d have to say that version 16 was pretty damned zippy.
With each annual release, Parallels is touted as being faster than the previous year’s version.
