system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do apps or websites that have offerwalls know that you installed and ran an app on your device or completed the offer?
gpt
There’s usually account information associated, either with you or the app. 

When apps run, they can register details on your computer or device, and, of course, “call home.”

Some token or tag will be shared. It’s really that simple.