* Element: An element is a pure substance made up of only one type of atom (like gold, oxygen, or carbon).

* Compound: A compound is formed when two or more different elements chemically combine in a fixed ratio (like salt, water, or carbon dioxide). Salt is made of sodium (Na) and chlorine (Cl) atoms.

* Suspension: A suspension is a heterogeneous mixture where particles of one substance are suspended in another, and they can settle out over time (like sand in water).

* Heterogeneous Mixture: A heterogeneous mixture has parts with different properties and compositions. You can easily see the different parts.

* Homogeneous Mixture: A homogeneous mixture has a uniform composition throughout. You can't easily see the different parts.

* Colloid: A colloid is a heterogeneous mixture where particles are dispersed throughout another substance. The particles are larger than those in a solution but smaller than those in a suspension. They don't settle out easily (like milk or fog).

Key Takeaway: Salt is a compound because it is formed by the chemical combination of sodium and chlorine atoms in a fixed ratio.