Potatoes are split into three different classifications; starchy, waxy and all-purpose. These classifications are given based on their texture, starch content and moisture.
Every potato type falls somewhere along this spectrum.
Starchy potatoes
Starchy potatoes earned their name because of their high starch content. They have a thick, dry skin that absorbs oil and becomes crispy when fried. High in starch means low in moisture; as the outer layer becomes crispy, the flesh of the potato softens. These are good for fried potatoes.
Waxy potatoes
These are low in starch but high in moisture. In terms of appearance, their skin is much thinner. Unlike starchy ones which become soft when cooked, waxy potatoes hold their shape. This makes them good for making soups or stews, potato salads, or casseroles. In general, they are best used for roasting, boiling and slicing.
All-purpose potatoes
All-purpose potatoes are the best of both worlds. They fall between starchy and waxy on the potato spectrum because they have medium starch and moisture content. This makes them the most versatile potatoes for cooking because they can be substituted for recipes that require starchy or waxy potato types. Therefore, they can be used for roasting, mashing, pan frying, stewing, soups.