A pull request (PR) is a feature used in version control systems like GitHub or GitLab, allowing developers to propose changes to a codebase. When a developer completes a set of changes in a separate branch or fork, they create a pull request to merge these changes into the main branch or another target branch. The pull request process typically involves code review by peers or project maintainers, who can comment, suggest modifications, or approve the changes. This workflow enhances collaboration, code quality, and security by ensuring that all changes are reviewed before integration, reducing the risk of introducing vulnerabilities or errors into the project.