Asynchronous File Export allows you to get very large data sets as a single export file.
Async Export works by starting the export with a REST request (which keeps running as an asynchronous process on the server), tracking progress with another REST request, and getting the completed file with yet another REST request.
This way of using the REST API makes sure there are no technological timeout limits so you can get reports for as many issues as you need.
For Synchronous File Exports, please see here.