hello-worldis a simple example but imagine you have a complex application with a large number of dependencies and it is tied to a specific version of Python or Java. Then imagine you have a second app again tied to a specific, but different, version of Java or Python. Now you have to try and ensure these two (often conflicting) versions sit on the same host and play nice. In the world of containers these two versions can operate in complete isolation from one another. Bliss.