A SCOBY, which stands for Symbiotic Culture of Bacteria and Yeast, is a gelatinous mass used in the fermentation of kombucha, a popular fermented tea drink. The SCOBY is responsible for converting sugar into acids, gases, and alcohol, giving kombucha its unique flavor and effervescence. It consists of various strains of bacteria and yeast that work together in a symbiotic relationship. During the fermentation process, the SCOBY floats on the surface of the liquid, forming a protective barrier. It can be reused multiple times to brew new batches of kombucha, and it can also be shared with others who want to start their own fermentation process.