Campden tablets suppress yeast activity and can be used instead of heat pasteurizing your wine must or cider. Campden is also very useful in removing chloramines from city water supplies, highly recommended if using tap water in your brews.
Glycerin and Super-Smoother can smooth out a wine's flavor profile and make it ready to drink quicker. If you have some sharp flavor notes it can be helpful.
Potassium sorbate suppresses bacteria and is useful in stabilizing your wine from further fermentation activity.
Wine tannin adds that rich tannin feel to red wines.