A drawdown measures the loss from the highest point reached to a subsequent low. Distance from high is the current drawdown: how far today's price is below its highest close in the data.
A 50% drawdown needs a 100% gain to recover, which is why large drawdowns matter so much.
Why it matters
Volatility treats rises and falls alike; drawdown measures only the pain. It is closer to how investors experience risk, and many give up on an investment during a deep drawdown, locking in the loss.
General information, not advice.