In macOS, in applications that take advantage of this feature, every time you click "Save" in your document (or every hour or if there are many changes) a new version is generated internally, even if you apparently see a single file with the l last thing you saved.
To recover a previous version you just have to open the file you want to work on and go to File> Back to ...
A list will appear with all the versions so that you can retrieve the one you want (with the date and time it was recorded).
If you are not very sure of the date and time you can click on «Browse all versions» so that on the left you will have a view of the current document and on the right a view of all versions.
You just have to scroll through the different versions until you find the one you want.
You can retrieve that version of the document by clicking "Restore" or make a copy by pressing alt + restore, as a standalone document, in case you just want to take some of the content and not touch the rest of your latest version.
This ability has been around for a long time but it's those little wonders that go unnoticed.
