Here's why:

* Dissolved Ions: Salt water contains dissolved ions (charged particles). When salt (NaCl) dissolves in water, it breaks down into positively charged sodium ions (Na+) and negatively charged chloride ions (Cl-). These ions can move freely, carrying electrical charge.

* Free Charge Carriers: The presence of these mobile ions allows salt water to conduct electricity. The electric current is carried by the movement of these ions.

* Conductivity Increases with Salt Concentration: The more salt dissolved in the water, the higher the concentration of ions and the better the conductivity.

In contrast, pure water is a very poor conductor of electricity because it has very few free ions.