Distributed computing vs. Parallel computing

http://en.wikipedia.org/wiki/Distributed_system

 

Distributed computing is a form of parallel computing, but parallel computing is most commonly used to describe program parts running simultaneously on multiple processors in the same computer. Both types of processing require dividing a program into parts that can run simultaneously, but distributed programs often must deal with heterogeneous environments, network links of varing latencies, and unpredictable failure in the network or the computers.