Builds are processes that update existing resources and create new resources. You run builds against projects to create or modify workspace resources. The type of project determines the type of build. For example, when you run a build for a Java project, the build converts each Java source file (.java files) into one or more executable class files (.class files).
Note:
See the Eclipse Help for more information about builds.There are two kinds of builds:
Incremental builds, which update only the resources that have changed since the previous build.
Clean builds, which update all resources.
There are three ways to run builds:
Automatically, whenever resources are saved. Automatic builds are always incremental and always affect all projects in the workspace. You enable automatic builds from the Project menu by selecting Build Automatically.
Manually, by explicitly selecting a build menu option. You can run incremental or clean builds manually, for specific projects, or for the entire workspace.
Using a script via command line.