Compare this with glucose's molecular formula: C6H12O6. The lowest whole number ratio of that is C1H2O1, i.e. CH2O - this is the empirical formula for glucose.
Sorry, that's a bit of a tangent compared to your questions, but I had the sudden urge to express the above experience
Molecular formula tells us the number of atoms of each element we have in a compound e.g glucose is C6 H12 O6.
Empirical formula is the simplest whole number ratio of a compound. So for glucose, the most common number is 6. So it would be C H2 O