Now, how do banks operate in Australia? If you go, for example, to the Commonwealth Bank, there is just one queue to the tellers, regardless of the number of the tellers. Customers wait in the queue until a clerk in one of the tellers finishes with his or her work and asks the next customer in the queue. This is an amazing organisational innovation, because slower clerks, or clerks who have more work to do will not slow down the processing of the queue. In other words, the queue itself is always processed as fast as the resources available to the bank branch allow.
We can design a parallel computer program in a similar way. We may have a master process which organises the queue of tasks. Slave processes correspond to bank clerks working at the tellers. A slave process asks the master for a new task as soon as it has finished with the old one. This way faster processes do not have to wait for the slower ones, and the execution of the program proceeds as fast as possible, given available resources.