Small phones, or compact smartphones, have exactly the same features as the large ‘phablet’ devices being pushed by phone manufacturers. They’re just smaller.
This means you get less screen, and possibly shorter daily usage times thanks to there being less space for batteries. As screens are measured across their diagonal, a 5.5-inch phone can be significantly smaller than a 6-inch model, even though that doesn’t sound like much. But they do have advantages too.