The number your connection uses online. It gives away roughly where you are and usually changes over time. It identifies a line, not a person.
The drawing that proves the sentence above. It is the same card that is in the book.
Think of it as
a house number for your connection.
For example
A website greets you in the wrong language for your street but the right one for your city. It saw roughly where your line comes out, not who you are.
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.