GitHub Actions is an automation platform for GitHub repositories that allows users to build workflows to automate software tasks. It was introduced in 2019 and is based on Azure Pipelines. Workflows are configured using YAML files and can be triggered by events like push commits, pull requests, or scheduled times. Actions, which are reusable code components, can be used in workflows and are sourced from the GitHub marketplace or created by users. GitHub Actions is free for public repositories and offers paid plans for private repositories.