Like some others have said, it’s a docking port of some sorts but I’ve never seen it in practice. In our company we buy the universal hybrid usb C docks and they are great. The connector has also a more useful secondary USB C port which you can use for charging if the primary port dies for some reason, saved us on numerous occasions that way so the user can work while we prepare a replacement machine.

In a bold attempt to force people to switch to new docking stations and hence abandon the old ones (where you docked the notebook via a proprietary port on the bottom of the machine), the “new” generation of docking stations had kind of a lever that was pushed into this abomination of a usb-c/thunderbolt slot. When we rolled out these new docks quite some users got confused, as you still “click” in the notebook into the new dock, but additionally have to push in this kind of new “lever”. Also, users got confused where to plug in the usb-c cable when not using the new dock 😬