A full address: which method, which computer, which file. The part just before the first single slash is the real destination — the rest can be made to look like anything.
The drawing that proves the sentence above. It is the same card that is in the book.
Think of it as
house number, street and city — for a page.
For example
A message says your package is waiting at a very long address. Read the bit just before the first single slash — that is where it really goes.
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.