La Pousette Earring Backs/locking backs
The La Pousette back is a finely tooled and cleverly designed mechanical back. It features a spring loaded mechanism that is pressure activated. You pinch the back by the tabs thereby retracting small connections inside the back that contact the post. Releasing them engages the connection which holds the back tight to the post. The post also has a safety notch near the end. If the back was able to slide down the post it would catch at the notch without falling off.
Locking backs consist of thin domed shaped discs with a small hole which the earring posts can be pushed into.  One either side of the earring backing there are small notches which when compressed causes the hole to widen and the earring to come out.  A perfect solution for a secure backing, there is little chance of you losing your earrings if they are secured with this backing.  Earrings held in place with locking backs will also fit snugly against your ear,
Screw Back Earrings
The most secure type of earring back is the screw back. It consists of a threaded post and a nut that is spun on to the post up to the back of the ear lobe. It cannot be pulled off- it has to be fully unscrewed. This is both a blessing and a curse - much less likely that you will lose an earring, but more time consuming putting them on and taking them off. Screw backs therefore tend to be a good option only for high value earrings.
Another consideration is that depending on the size of the hole in your ears the threaded posts may cause some irritation as threads make them slightly thicker and ‘edgier’ than friction posts. In addition, the backs must be threaded carefully to avoid “stripping” the threads which would result in having to replace post.
Screw backing earrings, as the name implies, work with a post that is threaded, like a screw. The back is gently screwed onto these ridges for a slip-proof, tight fit. While these are one of the more secure varieties of earring back, the threaded post may be less comfortable for those with sensitive ears. Although they offer the extra bit of security, if you like switching your earrings every day, these earring backs are slightly more time-consuming to remove and put on however will give you great security
Push Lock/Friction Lock/La Poussette Backing 
Push lock backings sometimes referred to as friction lock or la poussette backings, are a mechanical earring back that offers the best of both worlds in terms of comfort and security. They consist of a flat metal backing with two tiny clutches, one on each side, the earring back remains securely in place until you gently squeeze the two clutches to release it. Unlike the friction back, the la poussette cannot gradually loosen with wear and cannot slide off if the earring is pulled. Additionally, the post used with this earring back type has a small groove towards the end that makes it extremely unlikely that the earring could slide off by accident. However, when you do want to remove the earring, the process is as simple and quick as if it were a friction back.