An index is a list of all the names, subjects, and concepts in a literary work that is intended to assist readers easily locate where they are discussed in the text. An index, which is usually placed at the conclusion of the text, does more than just list the material (a table of contents is for that), it also analyzes it. The headings used in the index need to be comprehensive enough to identify every topic covered by the text, but not so specific that they repeat information already given in the text. The objective of an index is to make finding materials easy for both readers and search engines. Readers will find the index useful for locating specific topics within the text. Search engines can use the index to help them classify documents. For example, if you were searching for all topics related to movies in an online library, you could enter "movies" as a keyword and this would return any pages with that word in the title or description. You could then click on these links to see whether they were actually relevant to your initial search. The structure of an index is very flexible. It can be divided into different sections, such as titles, authors, subject headings, keywords, and even page numbers. Each section should only include information that will help readers or search engines find other related items. For example, if there are several books about movies available from different authors, you could list each one separately in the index rather than including both texts under the same title.