Implied volatility is the volatility that when inputted in the Black-Scholes model, it returns the theoretical market price of a European option value.
I understand that implied volatility is not observable. However, we have access to option value in real life. How is the option value calculated in real life? All the while I thought that we need all inputs for Black-Scholes model to calculate option value. But in real life, it seems that it is different.