It is the quantitative parameter that tells about the efficiency of your catalyst in terms of reaction rate per unit time. Using this, we can make a comparative overview on our catalyst's superiority over others.

I would recommend you  to read more before asking such a question. Google is very helpful.

See review 

Turnover Rates in Heterogeneous Catalysis

M. Boudart

Chem. Rev., 1995, 95 (3), pp 661–666

I agree with Mr. Sengeni Anantharaj. It is the real reflection of the catalytic capacity of a catalyst, which is the very important evidence in comparison with its counterparts.

It is an important parameter of catalyst's activity in the process.

That gives you the efficiency of over other methods or in different conditions 

I agree,

It is the quantitative parameter evaluating the efficiency of homogeneous catalysts as well as heterogeneous ones. It is the more convenient parameter to compare catalysts efficiencies. Some times, when the TOF of an homogeneous catalyst is very high no need to turn them heterogeneous!!!