What is this connector for on laptops?

I've seen it many times, but what is it for?

You could hang a kind of lock there.

This is not a connection, but the mount point for a Kensigton lock.

You can use it to chain your notebook so that it doesn't get any legs

You can put a lock on it, which is connected to the metal frame of the laptop (Kensington Lock)

Then nobody can steal the laptop so easily as long as they don't have special tools.

For a Kensington lock. This allows the laptop to be connected to a place so that nobody can simply take it with them

The lock symbol refers to a mechanical anti-theft device similar to a bicycle lock.