Hot tubs are separate from the pool, run on a different system independently and and can be heated all the way up to 101 degrees farenheit fairly quickly.
They have 4-6 seats within them, and multiple seats with massaging and whirlpool functions. They can be used comfortably, no matter the outside temperature. On cooler Florida nights or in the freezing winter season of upstate NY, an outdoor hot tub is a real treat in the snow!
Whirlpool tubs attached to the pool usually run on the same heating system as the pool. They have benches and airjets for massaging and whirlpool functions, but maintain the same temperature as the attached heated pool, and the temperature can’t be raised like a hot tub would.