J2EE, or Java 2 Platform, Enterprise Edition, is a set of specifications that extend the Java programming language to support large-scale, multi-tiered, and distributed applications. It provides a robust environment for developing and running enterprise-level applications, including web services, enterprise applications, and middleware. The platform includes various components such as Servlets, JavaServer Pages (JSP), and Enterprise JavaBeans (EJB). These components help developers create scalable and secure applications that can handle a high volume of transactions and users, making J2EE a popular choice for businesses looking to build reliable software solutions.