JavaEE What is,Why we need it

General APIs

The Java EE APIs includes several technologies that extend the functionality of the base Java SE APIs.
Java EE 6 Platform Packages
Java EE 5 Platform Packages
javax.faces.*
This package defines the root of the JavaServer Faces (JSF) API. JSF is a technology for constructing user interfaces out of components
javax.faces.component.*
This package defines the component part of the JavaServer Faces (JSF) API. Since JSF is primarily component oriented, this is one of the core packages. The package overview contains a UML diagram of the component hierarchy.
javax.servlet.*
The servlet specification defines a set of APIs to service mainly HTTP requests. It includes the JavaServer Pages specification.
javax.enterprise.inject.*
These packages define the injection annotations for the contexts and Dependency Injection (CDI) API.
javax.enterprise.context.*
These packages define the context annotations and interfaces for the Contexts and Dependency Injection (CDI) API.
javax.ejb.*
The Enterprise JavaBean (EJB) specification defines a set of lightweight APIs that an object container (the EJB container) will support in order to provide transactions (using JTA), remote procedure calls (using RMI or RMI-IIOP), concurrency control, dependency injection and access control for business objects. This package contains the Enterprise JavaBeans classes and interfaces that define the contracts between the enterprise bean and its clients and between the enterprise bean and the ejb container.
javax.validation
This package contains the annotations and interfaces for the declarative validation support offered by the Bean Validation API. Bean Validation provides a unified way to provide constraints on beans (e.g. JPA model classes) that can be enforced cross-layer. In Java EE, JPA honors bean validation constraints in the persistence layer, while JSF does so in the view layer.
javax.persistence
This package contains the classes and interfaces that define the contracts between a persistence provider and the managed classes and the clients of the Java Persistence API (JPA).
javax.transaction
This package provides the Java Transaction API (JTA) API that contains the interfaces to interact with the transaction support offered by Java EE. Even though this API abstracts from the really low-level details, it is itself also considered somewhat low-level and the average application developer in Java EE is assumed to be relying on transparent handling of transactions by the higher level EJB abstractions.
javax.jms.*
This package defines the Java Message Service (JMS) API. The JMS API provides a common way for Java programs to create, send, receive and read an enterprise messaging system's messages.
javax.resource.*
This package defines the Java EE Connector Architecture (JCA) API. Java EE Connector Architecture (JCA) is a Java-based technology solution for connecting application servers and enterprise information systems (EIS) as part of enterprise application integration (EAI) solutions. This is a low-level API aimed at vendors that the average application developer typically does not come in contact with.