A repository manager allows to store and retrieve build artifacts. The most popular examples for repository manager are Maven Central Repository and jcenter at Bintray, which you can use to retrieve your dependencies for a Maven build.
Nexus Training Syllabus
What is a Repository Manager
What is Nexus
How to install Nexus in CentOS 7?
Types of repository in Nexus?
Overview of Nexus Dashboard
How to Create a users and roles in Nexus
Integration the Nexus with Maven