An Enterprise Resource Planning system (ERP) is a broad business management tool that works across numerous areas of the business, including accounting, purchasing, customer relationship management, and more. A Warehouse Management System (WMS) is focused on managing the production and movement of inventory in your supply chain, while communicating this data back to the ERP. In summary, an ERP system focuses on optimizing processes within a business, whereas a WMS focuses on optimizing them in a warehouse.