Quote Originally Posted by hydrocannabis
what is RO water?
Reverse Osmosis: water is passed through a semi-permeable membrane to remove particulate matter and chemicals. It is typically used for growing if your water source has a very high TDS concentration. If you have a lot of crud in your water, RO removes it and strips your water of everything in it.

what does it do to help the plants?
Nothing, or everything. As mentioned above, it is usually a means of cleaning a dirty water source.

and where can I get it?
You can purchase it from the grocery store, or buy a small system that you plumb to your sink for home use.