Employee turnover is the rate at which people leave a company over a period of time and have to be replaced, counting both voluntary and involuntary exits.
Turnover measures how many employees leave within a set period, usually a year. It includes people who resign and people who are let go, and it is often split into voluntary and involuntary to show what is really happening.
Some turnover is healthy, but high or rising turnover is expensive and usually a symptom of deeper problems with hiring, management, or experience. Tracking it, and knowing your rate, is the first step to bringing it down.