What make sea water salty?

Rain does not have dissolved salts but when it falls on the earth, it dissolves small amounts of minerals from the rocks and soil that the water passes through. There is not enough salt in lake and river water for us to taste it (usually) and rivers and lakes are constantly being replenished by water flowing in to them. When the rivers reach the sea, the water evaporates but leaves the dissolved minerals behind, so the sea is slowly getting ever so slightly more salty as rivers carry the dissolved minerals into it.

That's a good question like asking why sugar is sweet?

The oceans tend to collect all salts and minerals from the rivers and lakes. This can explain for the saltiness i guess

Because of lots of sodium chloride in it