A food is crisp if it is fairly hard, brittle and easily broken. Very fresh vegetables are crisp and thinly sliced, cooked potatoes are so crisp they are actually called potato crisps!
Potato crisps, or just chips, are thin slices of potato deep fried until they are crispy. They are sprinkled with salt and other flavours, and sold in foil packets. The most popular flavour besides plain is salt and vinegar.
