Layer styles are effects that are added on top of your layer. They are editable and can easily be toggled on and off. To add a layer style to a layer go to. You can also right-click a layer to access the layer styles.
When you have the layer styles window up, make sure that the Enable Effects item is checked.
There are a variety of effects and styles you can apply to a layer. When you add a style, your layer docker will show an extra "Fx" icon. This allows you to toggle the layer style effects on and off.
This feature was added to increase support for Adobe Photoshop. The features that are included mirror what that application supports.