In Azure Pipelines, triggers are mechanisms that initiate the execution of a pipeline in response to certain events or conditions. Triggers help automate the build, test, and deployment processes, allowing you to define when and how your pipeline runs. There are several types of triggers in Azure Pipelines:

1. Continuous Integration (CI) Trigger: This is the most common type of trigger. It starts a pipeline run whenever changes are pushed to a specific branch of a repository. CI triggers are useful for ensuring that your code is continuously built and tested whenever new changes are introduced.

2. Scheduled Trigger: This trigger allows you to specify a schedule for when a pipeline should run. You can set up daily, weekly, or custom schedules to control when your pipeline executes, even if there are no code changes.

3. Pull Request Trigger: This trigger starts a pipeline run when a pull request is opened or updated. It’s particularly useful for running tests and validations before merging code changes into the main branch.

4. Batch Changes Trigger: This trigger, available in multi-stage YAML pipelines, helps in optimizing pipeline runs. It waits for multiple changes to accumulate and then triggers a single run to process them together. This can be useful to prevent running multiple pipeline instances for small changes.

5. YAML Path Trigger: With this trigger, you can specify a file or folder path in your repository. The pipeline will trigger only if changes are made to the specified path. This is handy for running specific pipeline stages for certain files or folders.

6. External Repository Trigger: This trigger allows you to trigger a pipeline in one repository based on events from another repository. This is useful for scenarios where changes in one repository need to trigger actions in another.

Here’s an example of how a CI trigger is defined in a YAML pipeline configuration:

In this example, the pipeline will run whenever there are changes pushed to either the main branch or any branch that starts with feature/.

Keep in mind that Azure Pipelines gives you flexibility to define triggers based on your specific workflow and requirements. You can configure triggers using the Azure DevOps portal or by defining them directly in your pipeline’s YAML configuration.