They’re called Omega backs for a good reason. A hinge is attached to the clip which allows the clip to flip up from the back of the earring to the back of your earlobe. The clip usually takes the form of a hinged wire which looks like the Greek letter Omega ώ, hence the name.
Lever back: This style earring has a hook that goes through the pierced earlobe and is held in place by a hinged lever that is attached to the back of the earring. Omega Back: A hinged, "O" shaped lever on the back of the earring, near the bottom, which closes over the post to hold the earring in place.
Latch backs are generally used for hoop earrings only. Some latch-back earrings contain a hinged post that goes through the ear and then snaps into a notch on the other side of the earring to secure it into place. Other latch-back earrings have a post that doesn't move.
Some screw back earrings are actually partial screw backs, with such backs only the top quarter of the post is threaded, the earring post is also usually thinner. This makes for a more comfortable option that still has the benefit of providing your diamond stud earrings with plenty of security.