GitHub Actions - yibinericxia/documents GitHub Wiki
Introduction
It allows you to run pipelines to build, test and deploy your code.
Runner
An application running the assigned the pipeline (job).
GitHub Runner
The runner uses the pre-defined virtual machine provided by GitHub (in Azure cloud), thus no need to manage the underlying infrastructure. It may be constrained by their hardware (such as RAM/CPUs) and software/OS (such as Ubuntu).
Self-hosted Runner
The runner is hosted in your chosen environment, such as virtual machines in the cloud (AWS, Azure, GCP, etc) or on-prem server, so you can have more customization and control, especially for resource-intensive workflow, specific security requirements, complex environment configuration, etc.