GitHub Actions
workflow
.github/workflows/ 以下に置いたYAMLで記述される一連のactionの流れを定義したもの
trigger
action
再利用可能な処理をまとめたもの
Actions are individual tasks that you can combine to create jobs and customize your workflow. You can create your own actions, or use and customize actions shared by the GitHub community.
from https://docs.github.com/en/actions/creating-actions/about-actions
GitHubのリポジトリにホスティングして公開することもできるし、リポジトリ内に閉じたものを作ることもできる
If you're building an action that you don't plan to make available to the public, you can store the action's files in any location in your repository.
from https://docs.github.com/en/actions/creating-actions/about-actions#choosing-a-location-for-your-action