Haswell turbo boost?

People talk about the slight performance dip in the new Airs 1.3Ghz down from 1.8Ghz clocked but with Turbo boost to 2.6Ghz. What does this actually mean.

Will you ever see 2.6Ghz?

Is that a true figure? - Is it the same as having a 2.6Ghz computer?

Real world difference in app loading times or dropping in frames per second in light gaming?

Is this "turbo boost" only with heavy multitasking?

+ any more information about this would be excellent.