Can you explain what a Runner is in the context of GitLab CI/CD and how it is used?

A Runner in GitLab CI/CD is an agent that executes jobs from the pipeline. It runs scripts described in the .gitlab-ci.yml file on a specific machine or in a container.

A Runner can be:

• Shared (common for multiple projects)
• Specific (assigned to a particular project)

Using a Runner allows automating the build, test, and deployment of code. For example, you can set up a Runner on a server with the required environment, and it will automatically run tests and build the project whenever a commit is made to the repository.