My company laptop has some special software installed on my laptop that boots up together with Windows. Right before the Windows login, I have the option to log in from outside the corporate LAN (ie: from any internet connection). If I select that, I can login by VPN from anywhere.

The thing I don't understand is that I can log in from other corporate LANs without logging into them. For example, I can visit Microsoft HQ, connect my laptop to their LAN and without logging into the Microsoft LAN I can get an internet connection and connect to my company LAN.

How am I able to connect to the internet without logging in their LAN?