Imagine you’re just a kid, and that annoying Little Johnny who is trying to outsmart you asks you sheepishly: “Do you know what .planets are in our solar system? I bet you don’t!”.
Well you actually don’t know the answer, but you wouldn’t let Little Johnny get his victory, and so you make this your life goal to find out, and you ask your parents: “What are the .planets in our solar system?”. And well, your parents don’t know that either, so they go on and ask their parents, who happen to know the answer.
Now it’s your turn to smirk sheepishly back at Little Johnny and tell him what the answer is.
So now whenever someone asks you what are the .planets in our solar system, you have the answer, from your Grandparents.