Dear Learner,

Hope you are doing great.

Once we add the jar Hive adds the jars to the classpath and puts the JAR file in the distributed cache so it's availabe around the cluster.

DistributedCache is a facility provided by the Map-Reduce framework to cache files needed by applications. 

Once you cache a file for your job, hadoop framework will make it available on each and every data nodes (in file system, not in memory) where you map/reduce tasks are running.

Please let us know if you have any other concerns so we can help you out here.