* Pure Substance: A pure substance is made up of only one type of molecule. Examples include pure water (H₂O), pure salt (NaCl), or pure oxygen (O₂).

* Salt Water: Salt water is a mixture of two substances: salt (NaCl) and water (H₂O). The salt is dissolved in the water, but they remain distinct substances.

Therefore, salt water is classified as a mixture, specifically a solution.