Substances are made of matter, which is anything that has mass and takes up space. But let's go deeper than that! Matter is made up of tiny particles called atoms.

Here's a breakdown:

* Atoms: The fundamental building blocks of all matter. They are incredibly small and have a complex structure of protons, neutrons, and electrons.

* Elements: Pure substances made up of only one type of atom. For example, gold (Au) is made up of only gold atoms, and oxygen (O) is made up of only oxygen atoms.

* Molecules: Two or more atoms bonded together. These can be made up of the same type of atom (like oxygen gas, O2) or different types of atoms (like water, H2O).

* Compounds: Substances formed when two or more different elements chemically combine in a fixed ratio. For example, water is a compound because it's always made of two hydrogen atoms and one oxygen atom (H2O).

* Mixtures: Combinations of two or more substances that are not chemically bonded. They can be separated by physical means. For example, salt and pepper is a mixture.

So, in short:

* Substances are made of matter.

* Matter is made of atoms.

* Atoms can combine to form molecules and compounds.

This is a simplified explanation, but it gives you a good starting point to understand what substances are made of!