HTG Chlorine Catcher????

What exactly does this do? What does it filter? What does it not filter? Chlorine Catcher VS. Reverse Osmosis?

that removes chlorine and other chemicals,but still has ppm's of calcium and magnesium,other things.
a r/o removes 100 percent of everything.

thats a sweet site. I'm having difficulty telling the difference between the 85$ one and the 100$ one?? Also it looks like they have a piece to connect to the faucet with is convenient. +rep