In storm we have the following mapping
storm | real world
+++++++++++++++++++++
Worker | Java Process
Executor | Thread
Task | Running Object Methods (execute and so on)
Since there is no shared memory between processes (and machines too) in storm, you don't have shared values such as counters spread out in all bolts in your application. but you can have shared values in executors (threads) in ONE worker.
To dealing with shared values in all executors, you must use other tools such as distributed caches (Memcached, guava) or databases.
In storm i think it uses zookeeper to restore states after re-balance.