Bobbles can be used as decorative texture stitches within your knitting. They are frequently used in cable knitting to create focal points for the cables.
In the Tuckle pattern from Cosy Knits Louisa Harding has used them to create a circle of bobble hearts around the yoke of the sweater.
These are very small bobbles, also called nupps and are simple to create. You work 4 stitches from one stitch by knitting into the front, back, front and back of the same stitch. Then you lift the first 3 stitches over the last one to quickly decrease all those stitches again.