3 lessons
Encryption and how HTTPS keeps a connection private
Why plain HTTP is like a postcard anyone can read, and the clever math (public-key cryptography) that lets two strangers agree on a secret key in public.
Firewalls, and the attacks they defend against
How a firewall decides what traffic to let through, and simple explanations of DoS attacks, spoofing, and man-in-the-middle attacks.
Wi-Fi standards and real-world network performance
What those Wi-Fi generation names actually mean, and how to reason about why your real speed never quite matches the number on the box.