Working with the .gitlab-ci.yml file, Runners, and integrated features.
GitLab CI/CD is a powerful tool for Continuous Integration, Delivery, and Deployment that is built directly into the GitLab platform. This all-in-one approach provides a seamless experience, as your source code, CI/CD pipelines, and other DevOps features reside in a single application. The configuration for GitLab CI/CD is managed in a YAML file named `.gitlab-ci.yml` located in the root of your repository. This file defines the structure and order of your pipelines and determines what to execute using GitLab Runners. 'Runners' are the agents that execute your CI/CD jobs. You can use shared runners managed by GitLab, or you can set up your own specific runners on your infrastructure for more control. The `.gitlab-ci.yml` file is composed of jobs that are grouped into stages. All jobs in a single stage are executed in parallel, and stages are executed in sequential order. A key feature of GitLab CI/CD is its rich set of predefined variables and integrations. It has built-in support for Docker, allowing you to easily build and test containerized applications. It also includes features like Auto DevOps, which can automatically build, test, and deploy your application with little to no configuration, and Review Apps, which automatically deploy the code from a merge request to a live environment for easier review.