The Compiler Plugin is used to compile the sources of your project. The default compiler is javac and is used to compile Java sources. Also note that at present the default source setting is 1.5 and the default target setting is 1.5, independently of the JDK you run Maven with. If you want to change these defaults, you should set source and target as described in Setting the -source and -target of the Java Compiler.
Other compilers than javac can be used and work has already started on AspectJ, .NET, and C#.
This Compiler Plugin corresponds to Maven 1.x's Java Plugin.
NOTE: To know more about the JDK javac, please see: http://download.oracle.com/javase/6/docs/technotes/tools/windows/javac.html.
The Compiler Plugin has two goals. Both are already bound to their proper phases within the Maven Lifecycle and are therefore, automatically executed during their respective phases.
General instructions on how to use the Compiler Plugin can be found on the usage page. Some more specific use cases are described in the examples given below. Last but not least, users occasionally contribute additional examples, tips or errata to the plugin's wiki page.
In case you still have questions regarding the plugin's usage, please have a look at the FAQ and feel free to contact the user mailing list. The posts to the mailing list are archived and could already contain the answer to your question as part of an older thread. Hence, it is also worth browsing/searching the mail archive.
If you feel like the plugin is missing a feature or has a defect, you can fill a feature request or bug report in our issue tracker. When creating a new issue, please provide a comprehensive description of your concern. Especially for fixing bugs it is crucial that the developers can reproduce your problem. For this reason, entire debug logs, POMs or most preferably little demo projects attached to the issue are very much appreciated. Of course, patches are welcome, too. Contributors can check out the project from our source repository and will find supplementary information in the guide to helping with Maven.