Without Anonymization, every computer in the internet communicates using a traceable Address. That means:
the website visited,
the internet service provider (ISP),
and any eavesdropper on the internet connection
can determine which websites the user of a specific computer visits. Even the information which the user calls up can be intercepted and seen if encryption is not used.
Info: Leaving a data trail online...
JAP uses a single static address which is shared by many JAP users. That way neither the visited website, nor an eavesdropper can determine which user visited which website.