Photoshop layer styles are a popular way to add an effect to an image, for example adding a drop shadow, to layers in a non-destructive way. With the right knowledge and experience, any effect can be achieved.
A pattern overlay is used to add a pattern to a particular layer. Using Pattern Overlay in conjunction with other effects can help you create different styles, with depth.
1. Getting Started
Credits:
Created with images by Nebenbei - "background texture structure"