Sonatype Nexus 3 Concepts
External
Internal
Repository
A repository is the container for components provided to the user. Nexus supports three types of repositories: proxy, hosted and repository groups.
Blob Store
A blob store is a storage mechanism for the binary parts of the components and their assets. Each blob store can be used by one or multiple repositories and repository groups. The repository manager starts by default with a filesystem storage-based default blob store, present in the repository manager's data directory ($NEXUS_DATA/blobs).
Proxy Repository
A proxy repository is a repository that is linked to a remote repository. Any request for a component is verified against the local content of the proxy repository. If no local component is found, the request is forwarded to the remote repository. The component is then retrieved and stored locally in the repository manager, which acts as a cache. Subsequent requests for the same component are then fulfilled from the local storage.
Hosted Repository
A hosted repository is a repository that represents the authoritative location for the components stored in it. The Nexus repository manager comes with "maven-releases" and "maven-snapshots" hosted repositories pre-configured.