How can some applications download and install ffmpeg just with one click?

I have seen some applications that, as part of their setup process, offer a button to simply download and install ffmpg.

How can this be possible without the user consciously installing it from the ffmpeg developers page or using a proper installer?

Can I simply store a finished build of ffmpeg to be downloaded and automatically copied to a specific location on the user’s computer?

EDIT:

I have found a related question with some answers, but none has been accepted (How to install ffmpeg and an app together on a Mac?).

It will be fine for me to just ask the user if they agree to download it. Then the app will download my ffmpeg build (stored in my website) to be copied in one specific directory to not interfere with other ffmpeg installations.