Hot springs are hot water or gas that springs from nature.
Sento (Public baths), on the other hand, are public baths that lend hot water and take money.
In the old days, it was also called a bathhouse or a yuya. The custom of bathing is said to have spread throughout Japan along with Buddhism, but the beginning of the public bath is said to be a “yuya” that appeared in Kyoto in the late Heian period.