The internet stops at one box in your home. Wi-Fi is only the last hop to your device — and when it feels slow, that hop is usually the cause, not your provider.
The drawing that proves the sentence above. It is the same card that is in the book.
Think of it as
a radio station only your home can tune into.
For example
You watch a movie in the living room and it plays fine. You carry the phone to the far bedroom and it stops. Nothing broke — you just walked too far from the little box in the hallway.
This is one card out of 275.
The hundred words you meet most are free — the whole set, animated, in one file that works with no internet.
Volume 1 has all 275 in fifteen chapters, with Staying Safe the largest chapter on purpose.