Clarify description of GitHub Actions workflows

Rephrase explanation of GitHub Actions workflows for clarity.

Author: code-qtzl

src/content/11/en/part11b.md

@@ -9,7 +9,7 @@ lang: en
 
 Before we start playing with GitHub Actions, let's have a look at what they are and how do they work.
 
-GitHub Actions work on a basis of [workflows](https://docs.github.com/en/free-pro-team@latest/actions/learn-github-actions/introduction-to-github-actions#workflows). A workflow is a series of [jobs](https://docs.github.com/en/free-pro-team@latest/actions/learn-github-actions/introduction-to-github-actions#jobs) that are run when a certain triggering [event](https://docs.github.com/en/free-pro-team@latest/actions/learn-github-actions/introduction-to-github-actions#events) happens. The jobs that are run then themselves contain instructions for what GitHub Actions should do.
+GitHub Actions operate on [workflows](https://docs.github.com/en/free-pro-team@latest/actions/learn-github-actions/introduction-to-github-actions#workflows). A workflow is a series of [jobs](https://docs.github.com/en/free-pro-team@latest/actions/learn-github-actions/introduction-to-github-actions#jobs) that run when a specific [event](https://docs.github.com/en/free-pro-team@latest/actions/learn-github-actions/introduction-to-github-actions#events) triggers them. Each job contains its own set of instructions that tell GitHub Actions what to do.
 
 A typical execution of a workflow looks like this: