The Java 2 Platform, Enterprise Edition (J2EE) is a set of coordinated specifications and practices that together enable solutions for developing, deploying, and managing multi-tier server-centric applications. Building on the Java 2 Platform, Standard Edition (J2SE), the J2EE platform adds the capabilities necessary to provide a complete, stable, secure, and fast Java platform to the enterprise level. It provides value by significantly reducing the cost and complexity of developing and deploying multi-tier solutions, resulting in services that can be rapidly deployed and easily enhanced.
To put it another way, Sun merely organized the two packages so that J2EE contained those things more likely to be used at an "enterprise" level. That is, things frequently used at companies/corporations. Sort of subjective, but that's the idea.