Author-it maintains a single plain-text index for all objects that contains every publishable piece of text relating to those objects. For topics, this includes the topic text with all paragraph and style tagging removed. It also includes variable assignments in the format <variable>=assignment.
This index is for when you use Find and Replace or Object Search, and greatly speeds up the search functionality within Author and Contribute.
In rare circumstances, the text in the plain-text index may not match the actual text in the object, resulting in inaccurate search results. If you find you're not getting the correct or expected search results, you should use the Re-index Search option.