What are Duplicate Management rules in Salesforce?

Duplicate Management consists of two components:

1. Matching Rules: Define how Salesforce identifies potential duplicates by comparing field values. Standard matching rules exist for Contacts, Leads, and Accounts. Custom matching rules can use exact match, fuzzy match (for names), or phone/email match algorithms.
2. Duplicate Rules: Define what happens when a match is found. Actions: Block (prevent saving) or Allow with an alert (warn the user but allow saving). Duplicate rules can apply to all users or specific profiles, and can vary behaviour when records are created via API. Reports on duplicates can be generated to review flagged records.