A hot tub is basically a small pool filled with circulating, heated water. Hot tubs are made of wood. The words "hot tub" and "spa" are interchangeable. Long ago, a hot tub was referred to as a wooden barrel that only accommodated two bathers. Later, liners and jets were added. They were eventually referred to as "spas". There are many different benefits of a hot tub. Many use them to just sit back and unwind or relax. They also offer therapeutic benefits. People suffering from arthritis often use hot tubs because of the constant jets that circulate the heated water. This motion relaxes the muscles and allows for better movement.
Jacuzzi is a brand name, created by Rachele Jacuzzi. Technically speaking, Jacuzzi only describes hot tubs or spas made by the Jacuzzi Company. Jacuzzi is a leading spa manufacturer.