Qu'est-ce que « Realised volatility and variance » ?

The realised volatility of an asset over a period is the annualised standard deviation of its returns over that period, conventionally computed from daily log returns without subtracting the mean. Variance is its square. Implied volatility is a price set today; realised volatility is a statistic known afterwards; the difference between them is what a hedged option position earns or loses.