Explanation on the indexing process, updating the index:
An index is made of references that link to the items you index (files, emails, etc.). The items themselves (the real files, the real emails, etc.) are not in the index.
To update your index, Copernic Desktop Search scans the items you chose to index (emails, files, contacts, etc), in order to detect additions, deletions or modifications made since the last indexing process.
Copernic Desktop Search does not reindex everything. New items are indexed. Modified items are reindexed. But items that have not changed are not reindexed. While it updates the index, look at the status bar or Status window to verify whether it is indexing or only scanning items. "Scanning" means that it is verifying whether the item has been modified. "Indexing" means that Copernic Desktop Search is actually indexing the item.
For example, while scanning, the software detects that a file is no longer where it used to be. It thus deletes the reference to this file in the index. Then, it discovers new files in a folder so adds references to these new files in the index. If the scanning process does not reveal any modifications, it simply won't modify the index.