MOSFET DRIVER- HIGH side vs LOW side
A low side FET driver's circuitry is referenced to ground.  Therefore it's easy to interface to controllers or even logic signals.

A high side N-FET has its source flying up and down between ground and the drain voltage, maybe higher with parasitic ringing.  So does the source reference connection on the driver.

So a high side driver generally has level shifting circuitry that allows you to control Vgs even though the source is at high voltage.  It may also have features to help with bootstrapping the high voltage, or desat protection, etc.

For N-channel switch applications the high side driver may have a charge pump built in to allow it to drive the gate above the source.