Anyone with the link means exactly that, including whoever it gets forwarded to next. For anything private, share with named people instead and the link cannot travel.
The drawing that proves the sentence above. It is the same card that is in the book.
Think of it as
leaving a key that works for whoever holds it.
For example
You send a link to vacation photos to one friend. He forwards it to three people you have never met, and it works perfectly for all of them.
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.