In cybersecurity and DevOps, a 'runner' refers to a lightweight, agent-like component used in continuous integration and continuous deployment (CI/CD) systems, such as GitLab CI. The runner is responsible for executing automated jobs defined in a pipeline, including tasks like code compilation, testing, and deployment. Runners can be hosted on various environments, including local machines, virtual machines, or cloud services, and can run multiple jobs concurrently. They help automate repetitive processes, increase development efficiency, and ensure consistency across software builds and deployments. Proper runner configuration and security are essential to prevent unauthorized code execution and maintain pipeline integrity.