Why...thank you for that comment. Miso is a paste. You can find it at Asian markets in the refrigerated section. I make my own because I'm a curious cook.
It is made out of fermented soy beans and salt. The liquid that comes off of it while it is fermenting is called tamari, which is similar to soy sauce. Miso has a deep, earthy flavor. The older the miso, the more complex the taste. Most miso soup is made with white miso which is not aged for very long. so its milder in flavor. Miso can also be made out of other beans and grains. South River Miso makes some amazing different kinds of miso and I believe that they sell online:
https://www.southrivermiso.com/