There are two main types of potatoes - waxy and floury. Waxy are thin-skinned and hold their shape well after cooking, and floury potatoes have a thicker skin and get nice and fluffy inside after cooking (think your classic russet baked potato!). Because their flesh stays more intact after cooking, waxy potatoes work well in soups like this where the chunks are meant to be separate (as opposed to a blended soup for example). And, because they have thin skins, there is no need to peel them before adding them to the soup, saving you a lot of prep time! Examples of waxy potatoes include red potatoes, new potatoes, and fingerling potatoes. Here is a great article that talks more about waxy potatoes. In addition to waxy potatoes, you can also use yellow potatoes here (similar types may be labeled as Yukon gold or gold potatoes). Yellow potatoes are in between waxy and floury, making this a great all-purpose potato!