Data Deduplication is a technique or a process used and created to eliminate duplicate records. This is usually done by organizations to streamline their storage use, as well as minimizing bandwidth use that’ll make opening different objects, records, and fields in their CRM pages faster.
Custom report types are seldom used by Salesforce Admins to meet the needs of their users. Custom Report Types are not just templates intended to show the custom objects you created for your business but can also be configured to set custom views for standard objects (e.g. Contacts).
As a Salesforce Admin, it is one of your duties to make the best use of this readily available feature, to make sure that you will be able to minimize, identify, and fix any security risks that may come from outside or within your organization.