Suppose you want to use Hibernate in your project. You would simply add a new dependency to the dependencies section in pom.xml, as follows:
And that's it! You don't have to hunt around to know in which other JARs (and in which versions) you need to run Hibernate 3.0.3; Maven will do it for you!
That is sweet, and relieves great pain in larger projects with many tendrils to OSS jars.