Subscripts in a chemical equation tell you the number of atoms of each element present in a molecule or formula unit.

Here's a breakdown:

* Subscripts within a molecule or formula unit: Indicate the number of atoms of each element within that specific molecule or formula unit. For example, in H₂O (water), the subscript "2" tells you that there are two hydrogen atoms and one oxygen atom (implied, as the subscript is "1") in each water molecule.

* Subscripts outside parentheses: Apply to the entire group of atoms within the parentheses. For example, in (NH₄)₂SO₄ (ammonium sulfate), the subscript "2" outside the parentheses means there are two ammonium ions (NH₄⁺) in the formula.

Let me know if you'd like some examples to clarify further!