Shadows and inner Shadows have the same controls but work in different ways. Shadows render outside a layer, while Inner Shadows render inside a layer.
You can apply multiple shadows to the same layer, and control their colors, blending modes, X and Y positions, blur radius and spread.
Note: When you zoom out about 400%, shadows with a blur value will not show on the Canvas. This is to make sure documents using lots of shadows render quickly. This won’t affect any assets you export.