What is this port on the laptop?

What is this connection called and what is it good for?

That doesn't look like a connection to me.

Is more the place for a so-called "Kensington lock"

I think this is for a lock.

Kensington lock, so you can secure your laptop against theft with a wire
e.g. Something like that: https://www.reichelt.de/laptopschloss-schluessel-1-8-m-silber-n-nblkk1002me-p242638.html?PROVID=2788

The symbol and shape indicate a Kensington socket for a Kensington lock.

Like with a bicycle, you can "chain" your laptop and secure it against theft.