The ability to pre-populate controls is a win-win situation for both the makers and the users. The maker could potentially use a single app with similar fields for multiple reasons and the user has fewer fields to fill. This is an intro video which walks you through what all you can do. If you are interested in learning then click on the link below -
https://www.valointranet.com/blog/digital-work/pre-populate-powerapps-controls-using-url/
