I am new to maven. So I have a project with pom.xml file. So I ran that with maven and the build was successful. I have glassfish. Glassfish is already running separately. S
Additonnaly, you should have a glance at this StackOverflow thread, dealing with maven deployement in glassifsh : https://stackoverflow.com/a/1836691/1047365.
For further understanding of Maven, you should REALLY read this (free) book : http://www.sonatype.com/books/mvnref-book/reference/. This is THE reference for Maven.
We can explain you what Maven is doing, producing, etc ... but Sonatype made a great work and you'll probably learn more reading it than we could ever do !
Regards.