User Acceptance Testing (UAT) is where the end user tests that what they / a provider has built works as they want it too. This want / need is recorded in the the signed off blueprint.
In UAT it is possible to use real data or data created especially for the UAT (if a software solution)
For UAT to be a success it is vital that the testing team are fully trained on the solution and that they have many testing scenarios that replicate the day to day use of the solution to test with it.
Successful International Project Management 