Photoshop Layer Styles are a set of non-destructive effects—like shadows, glows, and bevels—that you can apply to a layer's content without permanently changing it. Because they are linked to the layer, any edits you make to the content will automatically update the style. How to Access Layer Styles
If you want to learn more about Photoshop layer styles, here are some additional resources: Cum Photoshop Layer Stylel