What is Verification vs Validation?
Verification asks: did we build the thing right — does it conform to specifications and requirements? (Internal, objective, QC territory.) Validation asks: did we build the right thing — does it satisfy the customer's actual need? (External, judged by the customer, the essence of Validate Scope and UAT.)
The order is fixed — verify, then validate — and the gap between them is where famous failures live: products perfectly built to specifications nobody should have written.
Worked example
A crane-scheduling system passes every verification test — all 212 requirements meet spec. In validation, the site foremen reject it in an hour: the workflow demands more clicks per lift than the whiteboard it replaces, so nobody will use it. Verified: fully. Validated: not remotely. The requirements were the defect — which is precisely the failure class validation exists to catch before go-live instead of after.