Until now whatever testing was conducted, it was done by the implementation team to make sure that they deliver the best project, but it is the business users who have the final say about the project. Their usage will decide the success of the project.
User Acceptance Testing is the kind of testing where the dashboard is released to a select set of users who will spend a good amount of time in testing the dashboard from all aspects. They will look at if the dashboard fulfills the requirements given in early stage of the project, if it produces the correct data, if it gives the analysis which they are looking for etc.
Another aspect of the UAT is to make end users comfortable so that they can easily understand the sheets which are developed. Once the testing is finished, user may and may not ask for changes. If they find a bug and ask for changes then bugs...