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No its not a binding agent. Cyanuric acid 'stabilizes' chlorine so that it doesn't burn off quickly in bright sunshine.

If you aren't set up to use gaseous chlorine then you must purchase your chlorine "bound" to some other substance. If you're using Trichlor or Dichlor then your chlorine is bound to cyanuric acid (in granules or pucks). When you add it to your pool you get chlorine and cyanuric acid (CYA). CYA is also called stabilizer/conditioner because it binds with chlorine in the pool, and while bound, the chlorine can't be degraded by ultraviolet light. On the down side, while bound, the chlorine can't kill germs either. Which is why SOME CYA is good and too much CYA is bad. When you continue to chlorinate with Trichlor/Dichlor, eventually you raise your CYA (stabilizer/conditioner) level too high and the chlorine in your pool becomes less effective at the same concentration because it spends more and more time bound to CYA molecules than it does free and available to oxidize germs or viruses. The higher you run your CYA, the higher you need to keep your free chlorine level to achieve the same effectiveness.

Calcium hypochlorite is chlorine bound to calcium (usually as a powder that the pool guys like to call "shock"), which eventually raises your calcium level to the point where problems arise. For instance, you can get a calcium ring around the edge of the water if you have tile. (High calcium doesn't impact a liner pool nearly as much as a concrete pool) The ring around the edge is really dependent upon the Saturation Index, which is ((PH) + (Alkalinity Factor) + (Temperature Factor) + (Calcium Factor) – (12.1)) A saturation Index of zero means that there’s no tendency of the water to deposit or dissolve calcium. As the PH goes up, or the Total Alkalinity goes up, or the temperature goes up, or the calcium level goes up, so goes the Saturation Index.

Sodium hypochlorite is chlorine bound to salt in a water solution (commonly called liquid chlorine), which increases the salt content of your pool. Salt is not particularly bad, even in very high concentrations. The main drawback of “liquid chlorine” is that it is extremely high in PH and will tend to drive your PH and total alkalinity higher. Combined with water high in calcium and a concrete pool, and you have a high potential to end up with a calcium ring around the tile. Keeping your PH low when your calcium level is high is critical.

Lithium hypochlorite is chlorine bound to lithium, which adds lithium to your pool. Not particularly bad, but it's quite a bit more expensive than the other chlorinators available.

The point of all of that is this... When you purchase chlorine, if it is not bound to something then it is in gaseous form, which is quite dangerous and is normally only used by large commercial pools. When the chlorine is in your pool it is continually bound/unbound to cyanuric acid. While it's bound it won't be destroyed by the Sun, and while its unbound it can kill germs and viruses.

It can be added alone (to use with non-stabilized chlorine) or it can be added into the granules/pucks by the manufacturer and sold as 'stablized chlorine.'

Yes, cyanuric acid can be added alone. It is a stable solid at atmospheric pressure and temperature. But chlorine cannot be added "alone" by a home pool owner under normal circumstances. It must be purchased "bound" to some other "goo." And in the case of cyanuric acid (Trichlor or Dichlor), or calcium (Calcium Hypochlorite), eventually you get too much "goo" in your pool. Keep in mind also that "stabilized" chlorine (Trichlor/Dichlor) and "un-stabilized" chlorine (CalHypo/SodiumHypo/LithiumHypo/GasousChlor) are all the same thing once they're in your pool. Your pool already has stablilzer (presumably) and so the non-stabilized chlorine will be stabilized once it's in the pool, because the pool already contains plenty of cyanuric acid. The "source" of the chlorine is meaningless at that point, other than the fact that if you added the chlorine as Trichlor or Dichlor, then you added a small amount of stabilizer to the pool at the same time. But once in the pool it's all the same. Chlorine is chlorine.

Personally, I chlorinate with 10% sodium hypochlorite (liquid chlorine) and use 1" Trichlor pucks in a floating feeder when the water is particularly warm and needs an extra kick. I try not to let my cyanuric acid level get above 60-70 ppm though, so I use Trichlor sparingly.

My pool as of yesterday...

PH = 7.2
Free Chlorine = 2ppm
Combine Chlorine = 0ppm
Calcium Hardness = 450ppm (yuck)
Cyanuric Acid = 40ppm
Total Alkalinity = 100
Temperature - 75deg/f

That works out to a saturation index of about zero.

BTW, I never understood why people would actually purchase cyanuric acid separately since you can just chlorinate with Trichlor or Dichlor and you'll soon have more cyanuric acid than you want in your pool.

Regarding pool stores and all of the goo they'll sell you, I have been doing this long enough to have seen many gullible people walk into a pool store and get taken for a ride. For instance, their cyanuric acid level is already at 200ppm and what do they get sold? Trichlor! At 200ppm CYA they'd have to run their chlorine at 8-10ppm to kill harmful bacteria and viruses, and yet they get sold the exact thing that is causing their problems in the first place. Or how about people who go in and their calcuim level is already at 600 ppm in a concrete pool, and what do they get sold? CalHypo! With no thought of what their saturation index has risen to they get sold more calcium.

OK, I have to stop. I've eaten up much of my morning already. :) Gotta go for a swim!