Hookless is the future of low pressure, high-volume tires. It's a tubeless specific design that is generally stronger and lighter than a hooked clincher design. The tire is held in place by its bead, a "shelf" in the rim and air pressure. This is how tires and wheels are designed in the automotive world as well.
Hooked beads use a "hook' on the inner wall of the rim that coincides to a ridge on the tire bead. Hooked rims use this system to hold the tire in place along with, historically, the pressure of an innertube.
Why choose one over the other?
Hookless rims are great for high volume / low pressure situations and for tubeless tires ONLY. When a tubeless tire inflates, it wants to do two things. The air pressure wants to move the tire outward, and the bead wants to compress. You may notice that the bead seat shelf on the has a downward angle. This means as the air pressure moves the tire out of the center channel, the tires snap into place and lock into the bead shelf. This is the loud snapping sound you hear when you inflate tubeless tires.
At some point however, the outward force of the air pressure will overcome the strength of the bead and this is where you can have a tire that blows off the rim. As long as you are not approaching the strength of the bead with the amount of air pressure, the tire is held super secure, and the rim strength is improved. This is great for larger tires (gravel, CX, MTB) that will be used in places where the rims can have large impacts.
Hooked rims are great for low volume / high pressure. This is going to be your road tires that are pumped up to 65PSI or more. As the air pressure increases and puts more pressure on the bead of the tire, having the hook to hold that bead in place is helpful. If you are planning on running over 65PSI, then you should choose a hooked rim. This means if your wheelset is going to pull double duty of being both a road and gravel set, you will want to opt for the hooked rim profile.