Here's why:
* Fe stands for the element Iron.
* O stands for the element Oxygen.
* The subscript 2 indicates that there are two iron atoms in the compound.
* The subscript 3 indicates that there are three oxygen atoms in the compound.
Important Note: There is also a compound called Iron(II) oxide, with the formula FeO. The Roman numeral in the name indicates the charge of the iron ion. Fe₂O₃ is iron in its +3 oxidation state, while FeO is iron in its +2 oxidation state.