What is the difference between Jasper Reports and Ad Hoc View?

The Ad Hoc View lets you easily create and edit views and then use them to create reports.

To create a view:

1) Select a Topic or Domain (each of which defines a query and data source, and a view type)

2) Select the fields in your data source that should appear in your view.

The Ad Hoc Editor's interactive display of your results lets you evaluate your design without having to run the entire data set first. Finally, you can save the view, create one or more reports from it, and export it to several file formats. 

As a data explorer, the Ad Hoc Editor provides analysis options (such as Slice, Pivot, and Filter) to help you recognize trends and outliers in your data. You can drill into specific details or analyze your data at a very high level. For example, you might create a crosstab that shows the kinds of products a customer purchases together. 

Jaspersoft Report:  Domains -> Topics -> Ad Hoc View -> Report 

Every report created will have a corresponding "Ad Hoc View"?

     Yes by default, but you can create more than one report for each Ad Hoc View.

Will the view of Ad-Hoc reports following each report in the repository be permanent?

       Yes, and you can also create multiple reports from a single Ad Hoc View Report as mentioned above.

Are customized and specialized Domains still available after the upgrade to Jasper 5?

       Yes. All reports, custom domains, and any existing schedules will be moved to Jasper 5.