A filtered Report is a report that will show only specific elements from the complete scan (that you setup prior to the scan). If you select "filtered report" in the "Reporting" tab of the scan configuration screen, you will see filtering options appearing, see the filtering options in the screenshot below:

A differential Report is a report that will show the differences between the previous and current scan (latest scan). So for the same scan that you would have launched twice at different dates, the differential report will point out the differences between the first and second time you launched it (remediated vulnerabilities, new vulnerabilities, new hosts, etc.).

A remediation Report is a report that focusses on the remediation without providing as many details on the hosts and vulnerabilities as a regular report would provide. The purpose of this report is to solely provide the information that will allow someone to remediate the vulnerabilities.

A complete Report is a report that will show all the vulnerabilities and provide details on all of them as well as information on the hosts detected. The report is therefore said as being complete.