Concurrency vs Parallelism

Taken From Blog by Robert Harper: http://existentialtype.wordpress.com/2011/03/17/parallelism-is-not-concurrency/

Concurrency : It is about managing the non deterministic composition of components of programs. Example: A user types on key board the display should respond as quickly as possible, at same time it can also play music. These activities are non deterministic in nature , and we must respond to them as they occur.

Parallelism: With Asymptotic efficiency of programs with deterministic behavior. Example: Parallelism is about dependencies among the sub computations of a deterministic computation. The result is deterministic and there are many ways of achieving that. Some more efficient than others.

Concurrency is part of parallelism and also part of sequentiality