Microsoft-hosted CI/CD provides a pool of Windows, Linux, and Mac machines run and managed by Microsoft to create your builds and deploy your releases. Every Azure DevOps organization starts with the Free Tier of Microsoft-hosted CI/CD, so that you can run one build or release job at a time, for up to 1800 minutes of execution time each month.
If the free tier doesn't meet your needs, you can pay per parallel job with no monthly time limits. The more parallel jobs you choose, the more build or release jobs you can run at a time.
For Azure Pipelines CI/CD on machines that you manage, see self-hosted CI/CD. If you have custom software that needs to run as part of your build or in the deployment of your release then you will need to use self-hosted CI/CD.
To view the number of pipelines purchased, open the Retention and parallel jobs section of the Settings page, and select Parallel jobs.
For more information please read: Microsoft-hosted CI/CD in Azure Pipelines.