IV (implied volatility) is market nervous/uncertainty measure of a particular ticker. Think of it like the VIX but for a single ticker. It goes up during periods of uncertainty for that ticker and this causes the prices for options premiums to rise. For example earnings announcement would cause a spike in that week's IV for that ticker. Here it is in pictures using NFLX as an example.
Also watch the 11 minute video for much more details and possible trade idea.