GitHub Actions is a continuous integration and continuous delivery (CI/CD) platform that allows you to automate your build, test, and deployment pipeline. It is a tool that brings automation directly into the software development lifecycle on GitHub via event-driven triggers. With GitHub Actions, you can create workflows that build and test every pull request to your repository, or deploy merged pull requests to production. You can also run workflows when other events happen in your repository, such as creating a new issue.

An action is a custom application for the GitHub Actions platform that performs a complex but frequently repeated task. You can use an action to help reduce the amount of repetitive code that you write in your workflow files. An action can pull your git repository from GitHub, set up the correct toolchain for your build environment, or set up the authentication to your cloud provider. You can write your own actions, or you can find actions to use in your workflows in the GitHub Marketplace.

GitHub Actions is a CI/CD tool for the GitHub flow. You can use it to integrate and deploy code changes to a third-party cloud application platform as well as test, track, and manage code changes. GitHub Actions also supports third-party CI/CD tools, the container platform Docker, and other automation platforms.

In summary, GitHub Actions is a powerful tool that allows developers to automate their workflows across issues, pull requests, and more, plus native CI/CD functionality. It can help reduce repetitive code and speed up software development by creating a standardized and secure software delivery pipeline.