ELI5: Why was salt so valuable in ancient times if oceans are full of it?

Salt was extremely valuable in ancient times because it was the only way people could keep their food from rotting, and getting it out of the ocean was very hard work.

Imagine your kitchen today without a refrigerator. If you bought fresh meat or fish and left it on the counter, it would spoil and make you sick within a couple of days. Thousands of years ago, people did not have fridges or freezers, so winter or long journeys meant danger of starving.

Salt was their magical superhero for everyday survival:

• It stopped food from rotting: Rubbing thick layers of salt onto meat and fish sucked out all the moisture. Without water, tiny germs could not grow, allowing food to stay safe to eat for months.
• It kept people alive: Our bodies actually need a little bit of salt every day to help our muscles work and keep our blood healthy, especially when sweating during hard farm work.

• No ocean nearby: Most people lived far away from the sea. They had to travel on foot or ride horses across mountains and deserts just to reach it.
• Hard work to make: You cannot just scoop salt out of the water. Ancient people had to pour seawater into giant, shallow pools and wait weeks for the hot sun to dry up the water, leaving white crystals behind. If it rained, the work was ruined.
• Dangerous digging: The only other way was digging deep underground inside dark, dangerous salt mines.