What is the purpose of a Salt generator?

[CarlD]

No, it means you don't need to add as much chlorine, or as often. It won't save you money, but if set up and maintained properly it will save you time and allow you to leave your pool for a week or two at a time.

To start depends on the manufacturer, but usually you start with properly balanced water, then add enough salt to get the salt level to 3000ppm.

[JimK]

Also keep in mind a SWCG is best used to maintain chlorine levels, NOT to boost chlorine levels. Using a SWCG to boost chlorine levels will wear the cell out faster.