A pastry blender, as the name suggests, is a tool primarily used when making pies. It's used to combine cold butter and flour when making dough for pies, cookies, and other baked goods. It allows you to quickly, evenly, and efficiently incorporate cold butter, and helps prevent the dough from warming up, which is crucial for achieving a flaky texture in pies and cookies. Besides pies and cookies, it can also be used for making other baked goods like scones and biscuits. Additionally, a pastry blender can be used to smoothly mash potatoes.