Mathematica consists of two programs: the front-end, that provides the user interface, and the kernel, that performs of the computation tasks. These two programs communicate via the MathLink protocol, either on one computer or even across a network. It is now possible to run more than one Mathematica kernel at once. These kernels cannot only communicate with the front-end, but also with each other via MathLink. Hence, it is straight forward to distribute computations on several Mathematica kernels, thereby running Mathematica in parallel if several processors are at hand.
To facilitate the inter-kernel communication and the implementation of concurrent code, one can utilize the Parallel Toolkit add-on. We provide here a simple image processing example that runs in parallel on our Mathemaitca server bigmath.