what is gitlab runner and should we install it sepearately code example

Example: register runner gitlab

sudo gitlab-runner register
Please enter the gitlab-ci coordinator URL (e.g. https://gitlab.com ) e.g https://gitlab.com
Please enter the gitlab-ci token for this runner
Please enter the gitlab-ci description for this runner
Please enter the gitlab-ci tags for this runner (comma separated):my-tag,another-tag
Please enter the executor: ssh, docker+machine, docker-ssh+machine, kubernetes, docker, parallels, virtualbox, docker-ssh, shell: