If you're referring to sports, it helps your muscles and ligaments recover from exercising and injuries. It makes you stronger, with less effort and makes your body less injury prone. They are banned in all sports but there's ways to get around it. The only way to test now is blood test and most sports only allow urine tests.
Growth hormone, which is abbreviated as (GH) is a peptide hormone which is responsible in stimulating growth, cell duplicate and also renaissance in humans and other animals. Growth hormone is known to be a 191-amino acid, and you can find out more details on http://en.wikipedia.org/wiki/Growth_hormone.