The box that turns your provider's line into something your devices understand. In most homes it is built into the router, which is why one box appears to do both jobs.
The drawing that proves the sentence above. It is the same card that is in the book.
Think of it as
interpreter standing between two languages.
For example
The technician asks whether the lights on your box are green. That box is the one where the cable from the street comes into the house.
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.