Maven is a plug-in based software project management tool which core features are automation of your software build, dependency management, and generating of reports and documentation.
Use this tag if your question is related to the usage of Maven. As there exists different stable releases of this tool ensure that you make clear which version you are using. Also when your question is about a specific plug-in the version number of this plug-in might be useful for answering your question.
Before posting a question in this tag you should at least take a look at Sonatype's Maven Reference Documentation as it give you an good overview of Maven's concepts. There is also a section with a comparison between Maven and ANT.