YAML pipelines in Azure DevOps are a method for defining build, test, and deployment pipelines through code. YAML, which stands for “YAML Ain’t Markup Language,” is a human-readable data serialization standard that can be used to express the pipeline’s configuration. Here are some key aspects:

1. As Code Approach: YAML pipelines are defined in code, typically checked into source control, providing versioning, history, and collaboration capabilities.

2. Multi-Stage Pipelines: You can define multiple stages in a YAML pipeline, such as build, test, and deploy, and specify the tasks to be performed in each stage.

3. Extensibility and Flexibility: YAML pipelines offer flexibility in defining the exact steps and tasks required for your CI/CD process.

4. Reusability and Templates: Common steps and jobs can be defined as templates to be reused across multiple pipelines.

5. Parameterization and Variables: Parameters and variables can be used to make pipelines more dynamic and adaptable to different environments or configurations.

6. Integration with Azure DevOps Features: YAML pipelines integrate seamlessly with other Azure DevOps features like environments, approvals, and gates.

7. Support for Various Environments: They support deployment to different types of environments, including virtual machines, containers, and cloud services.

YAML pipelines provide a powerful, declarative, and version-controlled way to define your CI/CD processes in Azure DevOps.