One connection shared out to every device in the house. It is the first thing to restart when the internet misbehaves, and it has its own password worth changing.
The drawing that proves the sentence above. It is the same card that is in the book.
Think of it as
traffic constable at a household junction.
For example
The internet stops working and nothing you tap helps. You switch the little box in the hallway off, count to twenty, and switch it back on. It works again.
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.