A project is a group of source files and the settings with which you build, run, and debug those source files. In the IDE, all Java development has to take place within a project. For applications that involve large code bases, it is often advantageous to split your application source code into several projects.
The IDE builds its project infrastructure directly on top of Apache Ant, the leading build tool for Java applications. The IDE stores all of the information about your project in an Ant script, a properties file, and a few XML configuration files. This means that you can build and run your projects outside of the IDE exactly the same as inside the IDE.
The IDE includes several project templates designed to support different types of development including web applications, general Java applications, and so forth. The IDE's set of standard project templates automatically generate an Ant script and properties. The IDE also contains free-form project templates that you can use to base a project on an existing Ant script.
For more information about Ant, see: