Dishwasher Salt...

Who can honestly say they don’t have at least two big questions about dishwasher salt?

Where do I put? Why do I put it? How do I put it? When do I put it? Why is it so expensive? Why does it spill everywhere? How come the cap never does back on? How come the container is so hidden away?

The back of the packet says "you may have hard water - check the rocks and geology of your local area." So I've ordered a pick-axe, a canary, and a miner's lamp.