* Chemical Formula: A chemical formula represents the elements and their proportions in a compound. NaBr indicates that the compound is made up of sodium (Na) and bromine (Br) in a 1:1 ratio.

* Molecular Formula: A molecular formula specifies the exact number of atoms of each element in a molecule. While NaBr does represent a compound, it is ionic, meaning it's not made of discrete molecules.

* Unit: A unit refers to a specific quantity or measure. NaBr is not a unit, it represents a chemical substance.

In summary: NaBr is a chemical formula that describes the composition of sodium bromide, an ionic compound. It doesn't represent a molecular formula or a unit.