Can't understand vagrant ssh implementation - linux

Question

I recently start to use Vagrant (and recently move to Ubuntu from Windows too). My goal to understand fundamentals of vagrant ssh.
So, I'm trying to understand what vagrant ssh actually does.
I've read What does vagrant ssh actually do?, but I haven't understood anything.
I'll try to explain with an example:
The first time, I connect into the vagrant machine by ssh vagrant#192.168.0.x and typing the password.
Next, I configure the keypair and connect into guest by ssh vagrant#192.168.0.x without typing password.
Next, I try to understand how vagrant implements SSH into its own guest machine:
In /etc/ssh/sshd_config, I set PasswordAuthentication no, but vagrant ssh still works
Delete insecure_private_key placed in ~/.vagrant.d on the host machine, but vagrant restores it and vagrant ssh still works.
Remove openssh-server in the vagrant machine and now vagrant ssh really doesn't work :)
Please could anybody in plain English explain me how vagrant implements vagrant ssh?
Update: Vagrant Docs: SSH explains actually what I need.

Answer 1

May be I didn't get the point of your question, but I'll try to explain you the main differences between vagrant ssh and ssh.
vagrant ssh is actually the same as a normal ssh, but there are several differences between them:
port which ssh-client tries to access;
private key that ssh-client uses for authentication;
hosts-key is switched off for vagrant so you will not get initial message "The host is unknown";
other minor differences.
If you know the port where vagrant runs, and know where is the private key that vagrant uses,
you can use ssh instead of vagrant ssh.