An advanced planning system (APS) primarily differs from enterprise resource planning (ERP) by optimizing operations scheduling. APS is designed to provide optimization in scheduling, planning, and decision-making processes in areas such as production, logistics, and procurement. On the other hand, ERP focuses on integrating various business processes by facilitating the flow of information within an organization. Therefore, the key distinction is that APS aims to optimize operations scheduling, while ERP translates plans into actions and integrates various business functions.