What is a layer style?
Layer effects are linked to the layer contents. When you move or
edit the contents of the layer, the same effects are applied to the
modified contents. For example, if you apply a drop shadow to a
text layer and then add new text, the shadow is added automatically
to the new text.
A layer style is one or more effects applied to a layer or layer
group. You can apply one of the preset styles provided with
Photoshop or create a custom style using the Layer Style dialog
box. The layer effects icon appears to the right of the layer's
name in the Layers panel. You can expand the style in the Layers
panel to view or edit the effects that compose the style.