Missing translation in chapter 4.10 of manual
https://docs.gimp.org/2.10/it/gimp-tutorial-quickie-separate.html
On this italian page there are sentences in English
Sometimes you need to separate the subject of an image from its background. You may want to have the subject on a flat color, or keep the background transparent so you can use it on an existing background, or any other thing you have in mind. To do this, you must first use GIMP's selection tools to draw a selection around your subject. This is not an easy task, and selecting the correct tool is crucial. You have several tools to accomplish this: The «Free Select Tool» allows you to draw a border using either freehand or straight lines. Use this when the subject has a relatively simple shape. Read more about this tool here: Sezione 2.4, «Selezione a mano libera (lazo)» etc.