Verifying reviews means confirming that the reviewer actually performed the review for your journal(s).
Verification is a critical part rewarding reviewers and building your journal’s brand. There are 3 tiers of Publons verification.
1 Verified reviews from a Publons integration
When a researcher reviews for a partnered journal and opts in for recognition, we receive the review data directly from the journal’s EMS (e.g. ScholarOne Manuscripts or Editorial Manager) and can therefore be absolutely sure that review happened.
2 Email Auditing
Reviews can be added to Publons by researchers by forwarding their ‘Thank you for reviewing’ email to email@example.com. These are not verified by default. We audit the 'Thank you for reviewing' emails against key indicators to determine their legitimacy. If we cannot confirm an email's legitimacy we will contact the reviewer or editor and ask for additional evidence. We also randomly audit "Thank you for reviewing" emails by contacting the editor or journal administrator, and use this to build a network of trust.
You can read more here.