How did website accessed from pc automatically install mobizen on my phone?

I clicked on "Install" from my PC web browser for an application named Mobizen in the Google Play Store.  I was surprised when it prompted me to select a phone, and the only choice was the T-Mobile HTC One that I own.

And upon selecting the phone, this launched a process whereby Mobizen was downloaded automatically onto my phone.

Can someone please explain to me the specifics of how that works?