What does percent composition tell you about a molecule

Percent composition of a molecule is found through the molecular formula (Mass of each element found in a single mole of the molecule : total molar mass of the molecule). This tells you how much of a specific element makes up the molecule.

Also be aware that 2 molecules can have the same % composition but different formulas.

It tells you the ratio of the elements in the molecular formula. It gives you the total number of atoms in the molecule. It tells you how much of a molecule is made up of each element.