Hydraulic fracturing, AKA "fracking" is a process for squeezing oil and gas out of rocks. Its a dirty process, which contaminates ground water and has been found to cause earthquakes. In extreme cases, it has led to people being able to light their tapwater.
Oil companies have already used fracking in Taranaki, without resource consent. The Greens want to put a stop to this dirty and dangerous practice, and so they've started a petition calling on Parliament to impose a moratorium while the Parliamentary Commissioner for the Environment investigates its environmental effects. You can download and sign it here [PDF].