Oracle Retail Store Inventory Management (SIM) is a distributed client-server application that maintains optimal stock levels at stores. It has three layers - a presentation layer on the client side, a business layer, and a persistence layer on the server side interacting with a database layer. SIM uses a scalable and platform independent architecture with integration options that include RIB, RSL, web services, and file-based integration. It provides web services for item baskets and customer orders.