As eGroupware should host the addressbook of the whole organization, contacts might be created manually or important, with a higher risk to have duplicate entries...
The plugin allow to launch a deduplication analysis function, which is independant from the users' ACL and where the user may select or combine several fields (fist name, last name, emails, etc.)
The user may then select a view with the duplicates ; he then manually delete the duplicate or uses the function to merge the contacts and delete the first...