“ORP” stands for “Oxidation Reduction Potential,” and in simple terms means “antioxidants”. The most basic and powerful antioxidant there is is a negatively-charged electron. There are millions of these in every sip of ionized water. ORP is a measurement of whether a solution (in this case, water) has a tendency to either donate or take electrons from other solutions.
For our purposes, a negative ORP is very good, because it has lots of extra, negatively-charged electrons to fight free-radicals. Alkaline Water Ionizers can produce water with high negative ORP. Thest high levels of natural antioxidants in alkaline ionized water have important health considerations.
You can see the ORP-comparisons at point #18 in the chart, above.