Enterprise applications are designed to solve problems for large organizations and are multi-tiered, with functionality separated into isolated tiers like a client tier, middle tier, and data tier. The Java EE platform reduces the complexity of developing these large-scale, multi-tiered applications by providing APIs and services for tasks like security, reliability, and scalability so developers can focus on functionality. Tiered applications improve performance, scalability, and maintainability compared to traditional monolithic applications.