In one line
Implied volatility is the option's price restated as a rate of movement: the one number you can put into a pricing formula to get back the premium the market is actually charging.
How it works
A pricing model takes the index level, the strike, the time left, a rate and a volatility, and returns a price. Every input except volatility is known, so the calculation is run backwards: the market gives the price, and the number that reproduces it is the implied volatility. It is quoted as an annualised percentage.
That makes it a PRICE, not an opinion, and the distinction matters more than almost anything else in options. Implied volatility says what the market is charging for movement. Realised volatility says how much movement actually happened. The gap between them is the variance risk premium, and this desk measured it over 126 monthly cycles: on NIFTY the implied side sat about 1.6 volatility points above the realised side, and exceeded it in about three-quarters of cycles. Both of those are measurements about the past.
A level on its own means very little, which is why the desk shows a PERCENTILE beside it. Volatility at 14 meant something different in 2013 from what it means now, so the desk ranks today's reading against the past 252 sessions and prints where it sits. India VIX is the same idea computed by the exchange across the whole NIFTY chain rather than at one strike.
What it is not
Implied volatility is not a direction and it does not state the size of the next move. High implied volatility does not mean a large move happened afterwards; on this desk's own numbers it means the market charged more for one. It is also not comparable across indices without care: BANKNIFTY runs at a different level from NIFTY as a matter of course, so the same figure on the two boards is not the same reading.