A pattern is an image that is repeated, or tiled, when you use it to fill a layer or selection. Photoshop comes with a variety of preset patterns.
You can create new patterns and save them in libraries for use with different tools and commands. Preset patterns are displayed in pop‑up palettes in the options bar for the Paint Bucket, Pattern Stamp, Healing Brush, and Patch tools, as well as in the Layer Style dialog box. You can change how patterns are displayed in the pop‑up palettes by choosing a display option from the pop‑up palette menu. You can also manage pattern presets using the preset manager.
Photoshop also provides the Pattern Maker filter to create pattern presets, or fill a layer or selection with a custom pattern.