Imagine, we create at work at the same time a lot of projects, each project will likely cite some common jar package (.NET is dll file), One approach is for each project, a copy of these are dependent jar package (or dll file), this is clearly not good, the same file on your hard drive to save multiple copies, too occupied space, and versions of these dependent jar package (or dll file) is not very good management (such as a public jar package, upgrade from 1.0 to 2.0, all references to the project if the jar packages need to be updated, you must modify one project).
maven repository is a good solution to these problems, it creates a local repository on each machine, the machine all the project dependencies maven jar package unified management together, and these jar package with " coordinate" to uniquely identify (Note: the coordinate is another important concept to understand here simply as " uniquely identify a jar package file name, version number" logo can be), so that all maven projects do not need to copy the jar package as before lib directory, the entire maven project looks very cool.