Question

why sea water contains salt​

Answer 1

it contains mixed impurities which causes it's salty taste...

Answer 2

Ocean water contains lots of different mineral salts: sodium, chloride, sulfate, magnesium, calcium, potassium, bicarbonate and bromide. These salts enter the ocean through rivers, which pass over rocks and soil, picking up salt along the way.

This salt builds up in the ocean because the only way water can leave the ocean is through evaporation. And when the water evaporates it doesn't take the salt with it. So you end up with less water, and the same amount of salt, resulting in a pretty salty sea.