This method involves automating your deployment process so that you can deploy to production as soon as your code is ready. This way, you can easily roll out new versions of your application to production without any manual intervention.
There are lots of tools these days that allow you to do this, many of them are attached to your code repository like Github actions, Gitlab CI, CircleCI, TravisCI, Jenkins, etc. There are plenty of resources to help you get started with CI/CD.
CI is the method of ensuring that all code is tested and integrated into the main branch. CD is the method of ensuring that all code is deployed to production as soon as it's ready.