The indexation report, or coverage report, is the first cluster of technical reports in the GSC. Under Pages, it provides an overview of the indexed pages of a domain. As long as a page is not indexed, it cannot rank in the Google SERP and thus cannot generate organic traffic. Consequently, it is important to check whether all desired pages have been included in the index by Google. The report not only provides an overview of how many pages were indexed and how many were not, but also lists below how many URLs were not indexed and for what reason. You can export the report via the button at the top right and correct the reported errors.