The "Layer Style" is defined as the combination of effects on any given layer. There are different kinds of Layers Styles which are described as follows.

It allows you to add a drop shadow effect to any picture.

It allows you to add shadow effect inside any picture.

It allows you to create a glowing effect outside any image.

It allows you to create a glowing effect inside any image.

It allows you to create unique highlight and shadow effects on a layers contents.

When you create custom layer styles, you can use "Contours and Textures" to control the shape of Drop Shadow, Inner Shadow, Inner Glow, Outer Glow, Bevel and Emboss, and Satin effects over a given range.

It allows you to create wrinkled effect to any image.

It allows you to fill the layer contents with a solid color.

It allows you to fill the layer contents with a pre-defined gradients.

It allows you to fill the layer contents with a pattern.

It allows you to creates an outline on layer contents using a solid color, gradient, or pattern.

You can define the structure, element, quality, color etc., for the layers effects in the "layer style window".