There are many different names for Water Ionizers including: PH Water Machines, Alkaline Water Machines, Ionized Water Machines, Water Electrolysis Machines, etc.
Water Ionizers have electrode plates and perform electrolysis.
According to Wikipedia:
"Despite being described as 'water ionizers' the machines are designed to work as water electrolyzers. This is an electrochemical process in which water is split to form hydrogen and oxygen by an electric current. The overall chemical reaction is shown below:
2 H2O(l) → 2 H2(g) + O2(g)
During this process the water near the anode is acidic while the water near the cathode is alkaline. Water ionisers work by simply syphoning off the water near the cathode. This contains increased levels of hydroxide (OH−) and would be expected to have a higher pH (i.e. be more alkaline). The effectiveness of the process is debatable, as electrolysis requires significant amounts of time and power; hence the amount of hydroxide that could be generated in a fast moving stream of water (i.e. a running tap) would be minimal at best."
Hydroxyl ions or OH-negative in water act as antioxidants, they have an extra electron to donate.
Water (H20) contains both hydrogen (H+) and hydroxyl (OH-) ions. The pH of water is a measurement of the concentration of H+ ions, using a scale that ranges from 0 to 14. A pH of 7 is considered "neutral", since concentrations of H+ and OH- ions are equal. Liquids or substances with pH measurements below 7 are considered "acidic", and contain more H+ ions than OH- ions. Those with pH measurements above 7 are considered "basic" or "alkaline," and contain more OH- ions than H+ ions. For every one unit change in pH, there is approximately a ten-fold change in acidity or alkalinity. Therefore, a pH of 4 is 10 times more acidic than a pH of 5. Similarly, a pH of 9 is 10 times more alkaline than a pH of 8 and 100 times more alkaline than a pH of 7.
Source: Gov of Michigan
Whatever you'd like to call them, PH Water Machines restructure the water and you get a water with higher alkalinity and a higher concentration of Hydroxyl ions. This has been demonstrated to improve health and offer greater vitality. Purchasing a PH water machine is an easy way to boost your health. They also filter out impurities in your tap water.