Here's how to understand the formula:

* Co: Represents the element cobalt.

* 2: Indicates there are two cobalt atoms in the molecule.

* S: Represents the element sulfur.

* 3: Indicates there are three sulfur atoms in the molecule.

The Roman numeral "III" in the name "Cobalt(III) sulfide" indicates that cobalt has a +3 oxidation state in this compound. This is because sulfur typically has a -2 oxidation state, and to balance the charges in the compound, two cobalt atoms with a +3 charge each are required to balance the charge of three sulfur atoms with a -2 charge each.