Dropbox and Google Drive are the most popular file sharing services and widely used across the industry. They are used by the photographer to share the final pictures with the client or the model.
I personally use Dropbox to share my final images.
The photographer will send a link which either opens in a web browser, or, when installed, the Dropbox or Google Drive app on the mobile.
From either the app or web browser on your device, you can download single pictures / documents or the whole folder to your device.
If you simply want to receive files, you don't need to setup an account or even install an app: you can simply download the files from your devices web browser. However, if you also want to share files with others, you need to download an app for one of the services and create a free account.
If you are informed that the link contains the final images, please ensure that you download them to your device as soon as possible. It's highly likely that the photographer will remove the files from their Dropbox, and they will no longer be available for download.
Once the final pictures are delivered, do not edit them. The photographer and retoucher put in effort to express their artistic vision in the pictures. Avoid adding filters or cropping them without discussing it with the photographer first.