This is a common question. It stands for N-P-K or Nitrogen-Phosphurus-Pottasium (spelling???) I would reccomend you go organic.. I don't reccomend Miracle grow... Your Nutes depends on your what stage your in... If your in VEG, you need more Nitrogen so perhaps a ratio ROUGHLY of 2-1-1 (14-7-7,6-4-4), Check out http://www.foxfarmfertilizer.com/ look at GROW BIG, for flowering you need more Phosphorus I dont know the whole ratio, but there is also FOX FARM TIGER BLOOM which is 2-8-4, because you need more phosphurus for flowering.. Now I keep saying Tiger Farm products because that is what I bought, but when I went to the HYDRO store, the guy told me there is better stuff with more trace elements..There is like 100 + products you could buy,but I have heard good things about Fox Farm.. and its organic