The SCOBY is a Symbiotic Culture of Bacteria and Yeast which is the necessary component of the fermentation process. This culture consumes the sugar and tea in the sweet tea brew and over time ferments it to the taste of kombucha you are familiar with.
Package contains SCOBY and starter liquid. SCOBYs can last for many, many fermentations if you take good care of them. But if it begins to develop mold or you know it's become sluggish with its fermentations, it might be time for a fresh start.
Please note: your SCOBY may arrive with the pouch swollen. This is a common occurence and will not affect the health of the SCOBY or negatively affect fermentation.