A chastity cage is a metal, silicone, or resin “tube” that surrounds the cock and secures the balls with a ring. It has no components that target the asshole and just concentrates on containing the cock. It usually has a slit to urinate out of.
Cages are suitable for long-term wear since they are comfortable, safe, and allow men to perform required restroom duties without interference.
On the other hand, chastity belts are usually constructed of a combination of metal (most commonly stainless steel) and leather. It has a waistband and a strap that passes between the legs, including over the balls and assholes.
A little flap or “pouch” made of leather or a flat sheet of stainless steel holds the cock in place. Many male chastity belts have butt plugs put into the asshole and held in place tightly by the belt’s straps.
Male chastity belts are quite attractive, but because they restrict urinating or defection, as well as perhaps creating lines in the skin from their tight leather straps, they are best used for limited periods, usually only for the duration of a single-sex play session.
Now you know the difference, use each appropriately.