Quote from jenek-cowboy:
i am really happy that you at last understood me... And the method to estimate the IV is GARCH, isnt it?
GARCH is just one of the methods that some people use. There's no single method for estimating volatility.
I think part of the confusion comes from the fact that you use the term "implied volatility" all the time. Once again, the word "implied" is used only when you use market option prices and reverse the pricing model to arrive at volatility number that equates the theoretical price to the current market price.
If use GARCH or some other estimation method then you're estimating "future volatility" or "expected volatility" or simply "volatility", but NOT "implied volatility".