I’d like to add to Souvik’s answer: sodium is essential for life. Our bodies use sodium for transmitting nerve impulses – all the signals which our brain sends to muscles and other cells around the body require sodium. We lose a lot of sodium in our sweat so it’s important that we eat some salt in our foods. Sodium is also important to help maintain the salt balance in our blood. Too much salt is a bad thing though as it contributes to hypertension – high blood pressure.
We get salt from rock deposits of the mineral halite – which is basically composed of sodium chloride with some impurities. We have a big geological deposit of halite in southeast Antrim that has been mined commercially for years.