Nexus
In plain terms
A repository manager for storing and proxying dependencies.
Going deeper
Sonatype Nexus hosts and caches build artifacts and packages, acting as a central source for dependencies. It's an alternative to Artifactory.
Under the hood
Proxies public repositories and hosts private ones; supports many formats and security scanning.
Examples
Maven/npm/Docker repositories, dependency caching, private packages.
Think of it like...
Like a stocked supply depot that also fetches and caches parts from outside vendors.