"Indexing records" is a way to get document images (birth, marriage, death, military, etc) into a searchable format. As we research records on FamilySearch, Ancestry, and other places, we rely heavily on the availability of searchable records. As of August 2016, FamilySearch had 1.3+ billion records completed. There are ongoing projects for people to select from to help index records. Less than 25% of all the digital records in storage by the church are indexed. The problem is compounded by the fact that there are more NEW digital images added each day, than the number that are indexed. The LDS Church has created a way to make some of the non-indexed images available for review. Indexing is a great way to get your family members involved in doing family history. There are still BILLIONS of digitized images that need to be indexed so they can become searchable records. If short on time, work on a project in small time periods throughout the week until completed. Those who have spent time indexing these records are doing a great service to many, as those records are then searchable online. Indexing is one of the four aspects of doing family history work and carries the same blessings of having the Spirit of Elijah in their lives, and also the "protections" that our leaders have promised to those who participate in family history and temple work.
Commit to doing one batch per week for 6 weeks and you may just find this aspect of doing your family history quite rewarding!