Multi-thread in Single procerssor and Multi-processor

http://en.wikipedia.org/wiki/Thread_%28computer_science%29

 

On a single processor, Multithreading generally occurs by time-division multiplexing ("time slicing")in very much the same way as the parallel execution of multiple tasks: the processor switches between different threads. This context switching can happen so fast as to give the illusion of simultaneity to an end user. on a multiprocessor or multi-core system, threading can be achieved via multiprocessing, wherein different threads and processes can run literally simultaneously on different processors or cores.