Both are used across the range and the listing states which. Prongs hold each stone in its own small claw and let light in from the sides, but they sit proud of the metal, so they are also the part that catches on knitwear and wears down first.
Channel setting runs the stones between two walls of metal with no individual claws, which gives a smoother surface and far less to snag on a piece that meets doorframes and sleeves all day.
Bezel setting sits between the two, wrapping a rim of metal around each stone's edge. It guards the girdle well and gives a rounded outline, at some cost to how much light reaches the stone.