I had shared a basic understanding of maven sometime back.

http://kamalmeet.com/java/understanding-maven/

Here I will try to get into some more details.

As mentioned earlier we need a pom file for any maven project. POM stands for Project Object Model. It contains configuration details for the project.

To start with we provide basic info such as

<groupId>com.companyname.project-group</groupId>
<artifactId>project</artifactId>
<version>1.0</version>
 
group id: shows project group, say finance
artifact id: within group we will have a unique project name as artifact id say payroll
version: It is the release version e.g. 1.0 or 2.1.2 etc.
repositories: where all the jars, plugins and other artifacts are stored and used by maven.

<repositories>
<repository>
<id>custom.id</id>
<url>http://validrepo.com/mavenrepo</url>
</repository>
</repositories>

Type of repositories

Local Repository: A folder on local machine where all the dependencies are stored. Maven by default creates the repo in user/home directory, this path can be overridden by “localrepository” tag in POM.
Central repository: This is by default provided by maven, and has most of the common jars. No need for a separate configuration for this.
Remote Repository: Developer has an option to provide a repository explicitly, so if a give dependency is not found in central repository, it will be fetched from remote repository.

Dependencies: All the Jar files on which project is dependent and will be downloaded before the build.


<dependencies>
<dependency>
<groupId>test</groupId>
<artifactId>a</artifactId>
<version>1.2</version>
</dependency>