“What is the meaning of this?”
“What was this card doing in a book?”
“What’s it for?”
“What’s the point?”
Good questions all – cause questions get you moving, get you wondering.
The answers may be found in the quest.
Here’s an answer for you: Consider cards like this as keys. Keys to unlock things. They may all have a similar shape but some have different words underlined. So underlined = word key 🙂