Software Validation and Verification

Verification ensures that the final product satisfies or matches the original design (low-level checking) — i.e., you built the product right. This is done through static testing.

Validation checks that the product design satisfies or fits the intended usage (high-level checking) — i.e., you built the right product. This is done through dynamic testing and other forms of review.

According to the Capability Maturity Model (CMMI-SW v1.1), “Validation - The process of evaluating software during or at the end of the development process to determine whether it satisfies specified requirements. [IEEE-STD-610] Verification- The process of evaluating software to determine whether the products of a given development phase satisfy the conditions imposed at the start of that phase. [IEEE-STD-610]."

In other words, verification is ensuring that the product has been built according to the requirements and design specifications, while validation ensures that the product actually meets the user's needs, and that the specifications were correct in the first place. Verification ensures that ‘you built it right’. Validation confirms that the product, as provided, will fulfill its intended use. Validation ensures that ‘you built the right thing’.

http://en.wikipedia.org/wiki/Verification_and_Validation_%28software%29