If it's a supplement you're talking about, it(hopefully, if good one) will provide the necessary nutrients which may be lacking or imbalanced in the diet, which help hooves grow strong. I believe it's important to do at least a basic diet analysis before deciding on an *appropriate* nutritional supp for your particular horse.
I agree with the statement above, however, we have always used HB15. Makes a noticeable difference in their hooves and coat. I am sure there are better/different supplements out there, but this has worked for us.