GitLab Pipelines is a continuous integration/continuous deployment (CI/CD) tool provided by GitLab, a web-based DevOps platform. It allows developers to automate the build, test, and deployment processes of their applications. GitLab Pipelines uses a YAML configuration file, known as a `.gitlab-ci.yml`, to define the stages and steps of the CI/CD pipeline.

With GitLab Pipelines, developers can set up workflows that trigger automatically whenever changes are pushed to the repository. Each workflow consists of one or more jobs, which are individual units of work, such as building the application, running tests, or deploying to a specific environment. Jobs can be executed sequentially or in parallel, allowing for efficient and faster pipeline execution.

GitLab Pipelines provides a rich set of features, including predefined and custom-defined CI/CD variables, which enable flexible and dynamic pipeline configurations. It supports various stages and steps, such as code compilation, unit testing, code quality analysis, code coverage, and deployment to different environments. GitLab Pipelines also integrates with other GitLab features, such as code review, issue tracking, and project management, providing a seamless end-to-end development and deployment experience.

By using GitLab Pipelines, developers can ensure that their applications are automatically built, tested, and deployed in a consistent and repeatable manner. It promotes collaboration, streamlines the development process, and improves software quality by catching errors early and enabling faster feedback loops.