How files and layer work

We need some clear instructions on how QGIS files and layers work. It would be good to have some basic diagram of how files related to projects are organised and listed in the same folder and relative to the QGIS project on the PC. And then, when user wants to add a new layer, how they should do it (I know there is a section on it in the docs, but due to search and indexing, I never manage to find it).

The section can go here: https://merginmaps.com/docs/layer/best-practice/

Commencez par https://merginmaps.com/docs/layer/best-practice/ et examinez la documentation environnante pour trouver les indications existantes sur les fichiers de projet, les couches et l’ajout d’une couche. Le travail est terminé lorsque la section explique clairement l’organisation des fichiers et des couches, inclut le diagramme de base demandé et permet de trouver facilement les instructions pour ajouter une couche.