Stone fruits are usually classified as those fruit trees that produce fruit surrounding a large seed. Also included in this group are trees like apple a pear, which have a center core of smaller seeds.
They are deciduous, meaning that they lose their leaves in the winter. This allows them to survive cold winters. Stone fruits are also classified by how much cold they need in the winter time to successfully produce a fruit crop for the next spring or summer. Stone fruit varieties that do well in cold northern climates generally do not produce well in Tucson and the southwestern desert areas. And some, like most varieties of cherries, may not even grow here. Chill hours are usually defined by how many hours an area has below 40 degrees F during the winter season. In Tucson, that number is approximately 400 hours. Over the course of time, varieties have been discovered that may produce fruit well with even less than 400 chill hours.
And even more interesting, horticulturists have been crossing various stone fruits to create new varieties. Some of these are just starting to show up in fruits available at your local grocery store. Someone once describes this cross-breeding of fruit crops as the closest thing to sex in plants.