It’s likely that you’ll connect your Pi to a network so you can access the Pi from other computers, and vice versa. One of the best ways to communicate securely between two computers is via Secure Shell (SSH), a network protocol for secure data communication. Debian comes with everything you need to use SSH; you simply have to configure a few things.
If you only want to access other computers from the Pi, you don’t have to configure anything. For example, you can connect as the admin user to the host maik-schmidt.de by starting SSH on the Pi with the other computer’s name and password.
pi@raspberrypi ~ $ ssh firstname.lastname@example.org
Last login: ...