Compounds are generally described as having
1. an empirical formula, that is each element and the number of each element. For example, gasoline is composed of 8 carbon and 16 hydrogen atoms. The empirical formula is C8H16.
2. a structural formula, that is the spatial arrangement of the atoms which make up the compound. Ethane, for example, has two carbon atoms arranged in a straight line, and the two carbon atoms are surrounded by six hydrogen atoms. Its structural formula is
H - C - C - H