What is mag safe?

Mag Safe is the process of charging the phone by setting it on a Mag Safe Charger. Magnets on the device and the charger hold it in place. You then need only set the phone down on the charger and do not need to plug a cord into the device.

more or less yes, it makes alignment with the charger essentially automatic.

There are also some nice accessories you can find, such as car mounts and pop sockets that just hold to the iPhone using the internal magnets rather than cradles/clamps or adhesive.