Question
I just bought a new house that needs grass in the back yard. Some one told me that local landscapers, can produce a liquid product that they can just spray on your soil and grass will grow. Is that correct?

Answer
Yes, it抯 called Hydoseeding - http://en.wikipedia.org/wiki/Hydroseeding

It is a mixture of seeds, paper pulp and fertilizers.  It isn't the fastest way to get an "instant lawn", but it is pretty cost effective: About 15 to 20 cents/square foot, depending on the lawn variety and how much preparation is needed prior to application.   

The fastest way to get instant lawn is to lay down pre-grown sod, which runs about 25-35 cents/square foot, plus prep. costs.  ~M