Your foot is attached to the peddle.
Advantage - better at getting the power down.secure on hills especially when standing on the pedals. Knees and ankles are at the correct angle once correctly adjusted. They look the part
Disadvantage - hard to walk with spd-sl road shoes. Clipless moments.
I use normal peddles on my commuter and my feet move around. Hate it. Looking at mtb style cleats.
Best bike = spd-sl peddles and road shoes. LOVE IT!