The purpose of a Maven repository is to hold all software libraries used within an organization. The responsibility of a Build Artifact Repository Manager is to
1. Proxy content from remote artifact repositories .
The proxy functionality gives increased speed , better availability and makes it easier find and add dependencies to their projects (no more which repo holds artifactX?).
2. Share artifacts between developers .
The repository supports deployment of internal and external snapshots and releases and advanced security options can be to restrict access to sensitive artifacts. This functionality is required to work effectively with a large number of Maven projects and without it it is hard to implement the "one deployment unit, one Maven project" concept.
3. Make it easier to manage repositories and dependencies
The products often provide a graphical user interface that supports search and browsing of the repositories and functionality to view/add/delete artifacts.
Following is an alphabetical list of some repository managers we've heard mentioned around the Maven community: