Currency.

Your payment was wired. So, electrons. An idea. Information.

Don't get me wrong, I'm not going all Austrian School here, because gold and silver are simply ideas as well, because really, what is their value except for an agreement? Which changes daily. No. Wait, it changes by the minute.

My investments in companies have only meaning. It's not a real thing. My shares are held by a company. I have no physical representation of that except the statement from my broker. Well, I do have a couple of certificates, relics of an age long past, pretty script and curly cues, but still, just an idea, a contract, an agreement, that in a pinch, might as well line a bird cage.