In golf what is divot mix?

Divot mix is a mixture of sand as grass seed which is placed in fairway and tee box divots, the grass seed therefore grows and replaces at lost ground. There is however a lot of criticism about divot mix being used in the fairway, because you do not get a good enough strike and cannnot control the ball as well as you can from grass, most players say just get people to go get their divots.