Going by the formula, it is the percentage of the number of customers that you lost last quarter divided by the number of customers that you started with last quarter.
Simply saying, the churn rate is the rate at which customers stop doing business with an entity. It is most commonly expressed as the percentage of service subscribers who discontinue their subscriptions within a given time period. For a company to expand its clientele, its growth rate (measured by the number of new customers) must exceed its churn rate.
It is also the rate at which employees leave their jobs within a certain period. While the churn rate is also known as the rate of attrition or customer churn.