road clipless is meant for applications where youre spending more time on the bike than off. the cleat sticks out completely from the bottom giving you essentially a reverse heel. they are stiff and light and are meant for performance on the bike in mind, not walking.
road pedals typically clip in on only one side, and can have a higher adjustable tension for clipping in/out. it is "harder" to clip in to these quickly since the pedal is one sided and is more specific about the way the cleat enters the pedal
mtb style clipless is meant for applications where youre spending more time off the bike actually walking. typically the cleat is recessed into the shoe so you can walk normally, and are not as stiff. theyre mainly meant to keep your feet attached to the pedal, not necessarily for performance (though it will help dramatically)
mtb pedals usually clip in on both sides of the pedal (or 4 sides in the case of eggbeaters) and generally have a lower tension to clip in/out. mtb pedals are generally "easier" to clip into, most of the time you can blindly just step down onto the pedal to clip in