I would like to share the usage of parallel computing.

1. Save time-wall clock time-many processors work together.

2.  Can solve larger problems - larger than one processor's CPU and memory can   handle.

3. It provide concurrency - do multiple things at the same time: online access to databases, search engine Google's 4000 PC servers are one of the largest clusters in the world. 

4. It takes advantages of non-local resources by using computing resources on a wide area network or even internet (grid computing).

5. It is saving cost by using multiple "cheap" computing resources instead of a high-end CPU.

6. It overcomes the memory constraints for large problems using memories of multiple computers may overcome the memory constraints obstacle.