Fruit butter is a very thick, smooth fruit puree. It is made by slowly cooking fresh fruit with sugar until the fruit is so tender that it can easily be made into a puree. There is no butter in the recipe, and the name comes from the fact that puree has a smooth, silky texture to it. In terms of flavor, fruit butters have a very natural flavor to them because, although some sugar is added during cooking, the main ingredient is fresh fruit. Fruit butters typically are less sweet than jams and preserves are, and they are much smoother (and sweeter) than something like applesauce.
Fruit butters can be made with many different types of fruit. Apples, pears and pumpkins are very commonly used, but all stone fruits work well, as do some tropical fruits, such as mangoes. They are often spread on toast or used to top waffles, pancakes or scones. Fruit butters can also be used interchangeably with jams and preserves in some applications. You could use them on a peanut butter sandwich or as a filling in a baked good, for instance. But because fruit butters are much less sweet than preserves are, they can be showcased in recipes where you want the fruit flavor to stand out, like an Apple Butter Pie.