Enterprise JavaBeans (EJB) is a server-side software component that encapsulates business logic in Java applications. It simplifies the development of large-scale, distributed applications by providing built-in services such as transaction management, security, and concurrency control. EJBs are designed to be reusable and scalable, making them suitable for enterprise-level solutions. EJBs operate within a Java EE (Enterprise Edition) environment, allowing developers to focus on business logic rather than infrastructure concerns. They can be categorized into three types: Session Beans, Message-Driven Beans, and Entity Beans, each serving different purposes in application architecture.