Apollo, Aten and Armor are the three main classes of so-called near-Earth asteroids - those that come close to or cross Earth's orbit. The furthest out is the Armor group. These are asteroids whose orbits do no cross Earth's and are always further than our planet from the Sun. Apollo asteroids cross our orbit, but generally are found outside of it. And lastly, Aten asteroids also cross our orbit, and spend most time closer to the Sun than Earth. Each class is labelled for a prototype of the same name, 2062 Aten, 1862 Apollo and 774 Armor.