On trading forex, generally known as drawdown level. Simply put, it's the highest point of loss calculating from the first time trading activity. Generally measured with percentage.
For example, trader with Drawdown 60%, indicates there was previous loss with very high risk compared to their balance. Suppose you have deposit $100, with drawdown 50%, then most likely you will have the risk to put your account into danger 50% loss your money from initial deposit.
That's why. If you have a plan to follow someone, then you should look at drawdown level. Approximately 20%-30% drawdown is enough to label someone with low risk trading activity. Although there is no assurance, people with very small or lower drawdown will have low risk. As someday they could blow their account even though they had very low drawdown level. Well then how do we measure someone's trading activity FOR REAL?