The new WebLogic Server 12.2.1 Multi-tenant feature enables partitions to be created in a domain that are isolated from one another and able to be managed independently of one another. From a development perspective, this isolation opens up some interesting opportunities - for instance it enables the use of a single domain to be shared by multiple developers, working on the same application, without them needing to worry about collisions of URLs or cross accessing of resources.
The lifecycle of a partition can be managed independently of others so starting and stopping the partition to start and stop applications can be done with no impact on other users of the shared domain. A partition can be exported (unplugged) from a domain, including all of it's resources and application bits that are deployed, and imported (plugged) into a completely different domain to restore the exact same partition in the new location. This enables complete, working applications to be shared and moved between between different environments in a very straightforward manner.
At this point, all three instances of the same application are running independently on the same server and are accessible at the same time, essentially showing how a single domain can independently host multiple instances of the same application as it is being developed.