Maximum Turbo Frequency means that the value in question is the maximum frequency your processor is able to reach.
Please find information on Intel® Turbo Boost Technology here: http://www.intel.com/content/www/us/en/architecture-and-technology/turbo-boost/turbo-boost-technology.html
Consider it how fast the processor actually is.
The turbo boost function provides more of a power saving function than anything. Processors before turbo boost just performed to their maximum speed constantly, now they run at a slower speed to conserve power (amongst other reasons) and then run faster when needed by the applications running on the computer.
I've never quiet understood why Intel lead with the 'idle...ish ' speed, rather than the turbo boost frequency? Probally legal reasons i'm guessing?