How to Share a QGIS Project

A possibility is to save the project and all files (layers) to the same Geopackage file and send this.

As this sometimes can be a bit tricky, an even easier way is to create a zip folder containing project and data. See an example here: https://drive.switch.ch/index.php/s/kAXbCLWneg91kWY ( I used it today for this answer: https://gis.stackexchange.com/a/384194/88814). Unzip the folder, than open the project.

Be sure the have all files in the same folder or at least keep the same folder hierarchy whan saving as in the local project and activate rekative path in the settings. Otherwise, the files will not be found.

Always copy all files in the zip or Geopackage folder, not just the QGIS project (.qgz or .qgs files) - see here as well: Reordering layers in GeoPackage and changing the default naming in QGIS?. As you see in the screenshot, I added the project file + 5 Geopackage files and packed all together to a zip file: