What is Verification and validation?

Lots of tester have this question in there mind and some are confused that what is the difference between Verification and Validation.

Let me tell you that Verification and validation is the process of checking that a product, service, or system meets specifications and that it fulfills its intended purpose.

Verification is a Quality control process that is used to evaluate whether or not a product, service, or system complies with regulations, specifications, or conditions imposed at the start of a development phase. Verification can be in development, scale-up, or production. This is often an internal process.

Validation is Quality assurance process of establishing evidence that provides a high degree of assurance that a product, service, or system accomplishes its intended requirements. This often involves acceptance of fitness for purpose with end users and other product stakeholders.

It is sometimes said that validation can be expressed by the query "Are you building the right thing?" and verification by "Are you building the thing right?". "Building the right thing" refers back to the user's needs, while "building it right" checks that the specifications be correctly implemented by the system. In some contexts, it is required to have written requirements for both as well as formal procedures or protocols for determining compliance.