- Salt water is poured into a reservoir that is exposed to the sun.

- The salt water evaporates due to the heat from the sun.

- Leaving the salt behind (and most other impurities), the water vapor rises until it lands on the glass and condenses into water droplets.

- After enough builds up on the glass, gravity pulls the water droplets down the glass until they drop into a separate reservoir - not exposed to the sun. This water is desalinated and drinkable

It's efficient, cheap, slow, space consuming, simple and works well.