Question

Is salt a solution or mixture

Answer 1

Salt is a compound, with the chemical name "Sodium chloride"
and the chemical formula  NaCl.

Each molecule of salt is an atom of sodium electrically bound to
an atom of chlorine.  

The chemical properties of salt are completely different from the
chemical properties of either element in its molecule.  In fact,
sodium and chlorine are both toxic and corrosive, i.e., poison,
but as long as the salt is still salt, you can safely eat it !

There's nothing physical or mechanical, like spinning or filtering,
that you can do to salt to separate the sodium from the chlorine.
That takes electrical or chemical processes, and once you separate
them, you wind up with two substances that are both dangerous.

If you put salt into a jar with some sand and shake it up, then you
have a mixture.  The salt is still salt and the sand is still sand, and
they can be separated quite easily.

If you put some salt in some water, and stir it up so that the salt
dissolves, then you have a salt solution.  Some of the salt
molecules actually come apart in it, and there are sodium ions
and chlorine ions in the water.  When that happens, the water
begins to conduct electric current very nicely, and if you DO
pass current through it, you get sodium collecting at the end
of one wire, and chlorine collecting at the other wire.  But if you
just let it set there in the sun, or heat the solution on the stove,
then once the water evaporates, you have plain old salt again
in the jar. 

Answer 2

Depends on how you use the salt.
If you mix it with water it's a mixture because you can still seperate it, and it is still salt and water.