What are the differences between 12-2 and 12-3 Romex wiring and how do they impact electrical installations?

12-2 and 12-3 Romex wiring differ in the number of conductors they contain. 12-2 has two insulated conductors and one ground wire, while 12-3 has three insulated conductors and one ground wire. The main impact of this difference is that 12-3 wiring allows for an additional hot wire, enabling the installation of 3-way switches and multi-wire circuits. This provides more flexibility in electrical installations compared to 12-2 wiring.