@chu
Yes, they use quartz crystals.
It's a cool technology and has a bunch of advantages over previous watchmaking tech, like being able to use a battery to power it instead of having to carefully craft ways of storing winding energy. It's also intrinsically more accurate because the electrical timekeeping isn't affected by gravity variations, let alone engineering limitations. Plus it's cheaper to make.
I wonder if the point of advertising quartz movements is because such cheap watches couldn't possibly be any good if they were old style mechanical timepieces.