Glow is a steady light or illumination from an object. Usually it is not a very bright light, so it is easy to look at. glitter and sparkle mean about the same thing-- to reflect light intermittently. They do not refer to objects that make their own light. Twinkle means to appear to quickly change the degree of illumination from an object that gives off its own light. So this is usually applied to a star, especially when it is low on the horizon so it shines through a lot of atmosphere. If something twinkles it will draw the attention because usually light sources are steady.