Deploy Summary is a Vercel integration that analyzes pull requests and merge requests from GitHub and GitLab, detecting changed pages and providing detailed previews next to commits. These previews include screenshots of the changed pages, direct links to the changed pages, URLs of the deployment, and commit SHA. The integration enables team members to quickly review changes without needing to log in multiple times or visit different websites. To get started, users can visit the integration's page, add it to their account or team, connect their GitHub or GitLab account, create a new pull request or merge request, and analyze their deployment to see if any pages have changed. The integration aims to enhance workflows by providing additional features such as diff screenshots, lighthouse scores, and bundle sizes on pull or merge requests.