SNAPSHOT is a unique version that shows a current development copy. Unlike normal versions, Maven checks for a fresh SNAPSHOT version in an unknown repository for every build.
Now the data-service team will release SNAPSHOT of its updated code every time to a repository, say data-service: 1.0-SNAPSHOT, replacing an older SNAPSHOT jar.
We use it because we have different artifacts for different builds based on the same code. E.g. We might have one with debugging and one without. One for Java 5.0 and one for Java 6. Generally, it's simpler to have one build which does everything we need