SAPs products are in the Enterprise resource planning ERP business sector. The company's main product is SAP R/3, where the "R" stands for Realtime, the number 3 relates to the three tier application architecture: database, application server and client. The predecessor to R/3 was R/2. Other major offerings include APO (Advanced Planner and Optimizer), BW (Business Information Warehouse), CRM (Customer Relationship Management), SRM (Supplier Relationship Management), Human Resource Management Systems (HRMS) and KW (Knowledge Warehouse). The company also offers a new technology platform, named SAP NetWeaver. While its original products are mostly used by larger companies, SAP is now also offering products for small and medium sized enterprises (SME) with SAP Business One and SAP All In One.