Woodchips are used for smoking because they add flavor to the food. When you smoke with woodchips, you are essentially adding a smoky flavor to your food. This is why many people who enjoy smoked foods will use woodchips in their smoker.
There are different types of woodchips that you can use for smoking. The type of woodchip that you use will depend on the flavor that you are trying to achieve. For example, if you are looking for a sweeter flavor, you may want to use fruit wood chips. If you are looking for a more savory flavor, you may want to use hickory chips.