Back in ye olden days regular salt or sodium chloride was the usual choice for deicing roads and sidewalks. Now there are several deicer options, so you can choose the best deicer for your situation. The Transportation Research Board offers a tool to help you compare 42 deicer options based on price, environmental impact, temperature limit for melting snow or ice, and the infrastructure needed to use the product. For personal home or business use, you'll probably see only a few different products on the market, so here's a summary of some of the pros and cons of the common deicers:
sodium chloride (rock salt or halite)
Sodium chloride is inexpensive and helps keep moisture from accumulating on roads and walkways, but it is not an effective deicer at low temperatures [only good down to -9°C (15°F)], damages concrete, poisons the soil, and can kill plants and harm pets.
Calcium chloride works at very low temperatures and isn't as damaging to the soil and vegetation as sodium chloride, though it costs a bit more and may damage concrete. Calcium chloride attracts moisture, so it won't keep surfaces as dry as many other products. On the other hand, attracting moisture can be a good quality since calcium chloride releases heat when it reacts with water, so it can melt snow and ice on contact. All deicers must be in solution (liquid) in order to start working; calcium chloride can attract its own solvent. Magnesium chloride can do this too, though it isn't used as commonly as a deicer.
This is an amide/glycol mixture rather than a salt. It is supposed to be safer for plants and pets than salt-based deicers, though I don't know much about it otherwise, except that it is more expensive than salt.
Potassium chloride doesn't work at extremely low temperatures and may cost a little more than sodium chloride, but it is relatively kind to vegetation and concrete.
These products (e.g., Safe Walk) contain chlorides and work in very low temperatures, yet are supposed to be safe for yards and pets. They are expensive.
CMA or calcium magnesium acetate
CMA is safe for concrete and plants, but it is only good down to the same temperature as sodium chloride. CMA is better at preventing water from re-freezing than at melting snow and ice. CMA tends to leave a slush, which may be undesirable for sidewalks or driveways.
As you would imagine, calcium chloride is a popular low-temperature deicer. Potassium chloride is a popular warmer-winter choice. Many deicers are mixtures of different salts, so that you get some of the advantages and disadvantages of each chemical.