You can't use normal table salt in your water softener. The two primary options when it comes to your water softener and adding salt are potassium chloride and sodium chloride. Potassium chloride acts more like a conditioner, making it less efficient than sodium chloride.
However, the most popular types of salt for water softeners are evaporated salt and solar salt. These types of salt are all suitable for turning hard water into soft water, regardless of your water usage or your type of resin. They have a difference in terms of quality.
Evaporated salt pellets have the highest purity, making them the highest quality option if you're concerned about your water quality. Evaporated salt is also less likely to cause mushing or bridging when your unit is producing soft water. Solar salt crystals are still an effective means of treating hard water, but they're not quite as soluble.
Another salt for water softeners is rock salt. However, it's not best recommended for your water softener. This is because it contains more dirt and calcium sulfate, which doesn't dissolve effectively.