If you use Azure Pipelines for your pipelines, you can use a Microsoft-hosted agent to run your jobs. Maintenance and upgrades are handled automatically with Microsoft-hosted agents. You get a new virtual machine for each job in the pipeline each time you run it. After one job, the virtual machine is deleted (which means any change that a job makes to the virtual machine file system, such as checking out code, will be unavailable to the next job). Jobs can be run directly on a VM or in a container using Microsoft-hosted agents.
Azure Pipelines comes with a pre-defined agent pool called Azure Pipelines, which is made up of Microsoft-hosted agents.
Agents that are self-hosted
A self-hosted agent is a job-running agent that you set up and administer yourself. In Azure Pipelines and Azure DevOps Server (previously Team Foundation Server), you can employ self-hosted agents (TFS). Self-hosted agents provide you more control over the software you require for your builds and deployments by allowing you to install it yourself. Furthermore, machine-level caches and configuration are persistent from run to run, which can improve performance.