The Index Review tabs allow you to examine your index after it has been created. They provide statistics about the index as a whole and about individual content items. You can use this information for troubleshooting; for example, if a search does not return the expected results, has the index size changed? Are all expected languages and file formats included? Has the customization data changed? Are the expected content items included in the index? This information helps locate and identify indexing problems before they can affect your production site.