Salt - is the substance itself. A type of crystal that exists naturally, such as that in sea water.
Salty - usually describes a taste or smell. So you can say something like
"This popcorn tastes really salty!"
Saline - as an adjective, it simply describes a substance that contains salt. As a noun, saline is a solution of salt and water.
You most often hear the word "saline" when describing chemical compounds or when talking about the solution sometimes used in medical situations. "Saline" is mostly used in scientific situations.
Does this make sense? Let me know if you need more examples.