A wok stand is a device used to steady a round bottomed wok when used on a cooker top. On some hobs, a round bottomed wok can be very unstable and liable to tip over, something which is highly dangerous when hot oils are involved. Often a generic wok stand is provided with the wok itself. Some cooker manufacturers provide stands designed to fit the hob of specific cooker models.
A wok stand does not need to be used if you have a flat-bottomed wok as these are specifically designed for electric hobs.