Apps Script Course: Introduction
The programming language of Google Sheets used for writing macros is called Apps Script.
It's a completely different language from Excel's (VBA) as it is a modern version of JavaScript that benefits from many features and concepts of modern programming languages.
But if you have never used Apps Script (or JavaScript) before, don't worry, the course starts from zero with simple concepts and will gradually evolve through the lessons (which are strongly recommended to be followed in order).
Apps Script Editor
Open a new Google Sheets document and click on Extensions > Apps Script to access the Apps Script editor:
Note that you may sometimes have to wait a few seconds after opening the document to access the editor.
The editor then opens in a new tab, by default with an empty function:
Start
Click on the right arrow to move to the next page of the course.