ph water, meaning perfectly ph balanced water. tap water is fine, but you should let it sit, if possible 24 hours to let the clorine evaporate. you need to purchase a ph checker or you can go the cheaper route and buy dip sticks that check the ph... you can find them at your local grow shop or online. you want your ph in your water to be neutral around 7.0.
you can also use distilled water, that usually has a ph of 7.0 too but it can get expensive over time.
if your looking to grow decent product, i suggest you hit the books to find out some more info on growing, little things like ph make a huge difference when growing and it will give you more insite on what your actually getting yourself in to... it's a lot of work but the outcome is usually worth it.