* 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 elements chemically combine in a fixed ratio (like water (H₂O) or salt (NaCl)).

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

* Heterogeneous mixture: A heterogeneous mixture has a non-uniform composition. You can easily see the different parts.

Brine is typically salt (NaCl) dissolved in water (H₂O). The salt and water are evenly distributed, making it a homogeneous mixture. You can't see the individual salt particles in a well-mixed brine solution.