The following is an excerpt from an article by Sharon Howell published at https://www.familysearch.org/blog/en/explore-historical-images/:
“FamilySearch, FamilySearch partners, and volunteers worldwide have worked to make over 3 billion records easily findable online with a very simple name search. But did you know that these indexed records represent only 20 percent of the historical records FamilySearch has available online?
“If you haven’t found your ancestors by using the main search form on FamilySearch.org, it may be that their information is locked inside a waiting-to-be-indexed digital image. In 2018 alone, FamilySearch added over 432 million new record images to its online collections. But it can take years to catalog and index these images so they can be readily searched.
“Fortunately, the tools for finding the record image you need online are improving dramatically. Well ahead of any formal indexing or cataloging, the new FamilySearch Explore Historical Images tool can help you find records about your ancestors more easily, even when their information is not text-searchable and seems to be locked inside a digital image.”
You can read the full article at: https://www.familysearch.org/blog/en/explore-historical-images/.