Sonatype CLM - Repository Manager User Guide
Repository managers allow you to manage repositories filled with software components required for development, deployment, and provisioning. You can publish your own components to these repositories as well as automatically proxy external repositories like the Central Repository to provide efficient component access to your organization. In this role they fulfill a central part for component lifecycle management.
A repository manager greatly simplifies the maintenance of your own internal repositories, as well as access to external repositories. Using a repository manager is a recommended best practice for development efforts using Apache Maven or other build systems with declarative and automated transitive dependency management.
By proxying external repositories as well as providing a deployment target for internal components, a repository manager becomes the central and authoritative storage platform for all components. You can completely control access to, and deployment of, every component in your organization from a single location. It allows you to manage, which components get into your products from external sources as well as examine and keep track of components produced by your build systems. In terms of the incoming components, a repository manager allows you to secure the connection to an external repository and ensure that your component usage is not publicly exposed.
Just as Source Code Management (SCM) tools are designed to manage source code, repository managers have been designed to manage and track external dependencies and components generated by your build. They are an essential part of any enterprise or open-source software development effort, enabling greater collaboration between developers and wider distribution of all components. You benefit from increased build performance due to local component availability and reduced bandwidth needs by avoiding repeated downloads to your setup.
Note
The book Repository Management with Nexus provides an extensive introduction to repository management, its advantages and stages of adoptions for further reference. If this is your first introduction to repository management, there is a wealth of information, that expands beyond what we have provided here.