Parallel processing is the ability to perform multiple computations simultaneously.
In some multitasking operating environments, it may appear that you are computing two things at the same time, but in reality the computer is only doing one thing at a time, switching between tasks so quickly that it appears to be doing more than one thing at a time when it isn't. True parallel processing involves physically separate computing engines, each chewing on some computation. Since microprocessors were first invented, engineers and hobbyists have been envisioning a computer system consisting of many processing elements. However, advances in the performance of single processor units has been so great in such a short time that many engineers and scientists believe that uniprocessor computers will always provide the best performance and that higher performing computers are only a generation away. Yet parallel processing is starting to emerge as a way of bringing more computing power to bear against problems that even the fastest computers have found intractable.