Here's a breakdown:

* Solubility: A substance's ability to dissolve in a solvent (usually a liquid like water).

* Insoluble: A substance that does not dissolve in a particular solvent.

Examples of insoluble substances:

* Sand in water: Sand does not dissolve in water, it simply settles at the bottom.

* Oil in water: Oil and water are immiscible, meaning they do not mix or dissolve in each other.

* Plastic in water: Plastic is generally insoluble in water.

It's important to note that "not dissolving" doesn't necessarily mean a substance doesn't change at all. Some insoluble substances might still react with the solvent or undergo other physical changes.