Originally Posted by
Skies
First off, a little explanation of "Resonance". It's a property of anything that vibrates (that is, everything). If they're in the same frequency (or a multiple thereof) then they are resonating. RL crystals are, far as memory recalls, the solid material that resonates the easiest with human voice (as a curiosity). So the crystal-infused card and aetheryte resonating would mostly mean that the card has been 'registered' with the aetheryte.
Actually "Why can't I kill 8 moles before touching the card to the crystal", it's actually explained somewhere in-game or the flash site or somewhere else. Leves are 'permissions' (quite literally, a 'leve' is a very old word for permission) to do official work. Getting there and synching with the aetheryte is the equivalent of you going over to the officer there going "Bro, i'm here to do that job" and he says "Okay, go ahead" and you can do it officially.
Getting your rewards is, I presume, the function of the Aetherial Gate (which is... An extension of an Aetheryte far as I remember) that pops up. In function it looks like the leve card also serves as a 'homing point' for whatever arcane teleport spell that XIV uses.
And, well, that is how I understand it, at least.