For either type of glow, you may select the color used by clicking on the Glow Color button. The strength slider will control how large (how far from the element's edges) the glow will be.

An inner glow will create a glow that extends from the edge of the element inwards, fading as it gets away from the edge.

An outer glow will create a glow that extends from the edge of the element outwards, fading further away from the element.