Maven Snapshot Repository vs Release Repository

Release repositories hold releases and Snapshot repositories hold snapshots. In maven a snapshot is defined as an artifact with a version ending in -SNAPSHOT. When deployed, the snapshot is turned into a timestamp. By definition, snapshots are mutable, releases are immutable. This is why Nexus makes you store them separately because usually you don't care if you lose snapshots, but you will care if you lose releases. It makes snapshot cleanup much easier to deal with that way.

Release Artifacts

These are specific, point-in-time releases. Released artifacts are considered to be solid, stable, and perpetual in order to guarantee that builds which depend upon them are repeatable over time. Released JAR artifacts are associated with PGP signatures and checksums verify both the authenticity and integrity of the binary software artifact. The Central Maven repository stores release artifacts.

Snapshot Artifacts

Snapshots capture a work in progress and are used during development. A Snapshot artifact has both a version number such as “1.3.0” or “1.3” and a timestamp. For example, a snapshot artifact for commons-lang 1.3.0 might have the name commons-lang-1.3.0-20090314.182342-1.jar.

Taken from refcard