Pucks

[waterbear]

Dichlor and trichlor are both stabilzied chlorine (chlorinated isocyanurates). Trichlor has a pH of around 2 while dichlor has a pH of around 6 so both are acidic. Trichlor is slow dissolving so it is suitable for forming into tablets for use in erosion feeders. Dichlor is very fast dissolving so it is sold in granular form and is not really suitable for use in erosion feeders.
Dichlor adds more CYA to the water than trichlor. For every 1 ppm of FC added dichlor will add .9 ppm of CYA while trichlor will add .6 ppm.
Hope this helps.

Edit: some companies will include other ingredients such as copper sulfate as an algae preventative, clarifiers, sodium tetraborate (borax) as a pH buffer, etc. into their formulations of these products but these have nothing to do with whether it's trichlor or dichlor. Also, the number of chlorine molecules attacted to the cyanuate structure determine if its dichlor or trichlor. Dichlor has two and trichlor has three. This is why dichlor puts more stabilizer in the water then trichlor for a given amount of chlorine. There is one third more chlorine in trichlor than in dichlor.