[thaumasiotes]

It refers to whether the yogurt is alive or dead. It's not exactly mysterious terminology.

You get yogurt by using bacteria to process milk. In order to do their processing, the bacteria need to be alive. So, for example, adding living yogurt to milk will get you more yogurt, but adding dead yogurt to milk will get you milk with some dead yogurt in it.

[_moof]

I agree it's not mysterious. I was asking with some admittedly false naivety because if I'm being honest, I'm skeptical. I've only ever heard about this from people whose opinions on nutrition are dubious in other ways, and it's usually phrased as something like "all the yogurt you get from the store is dead." I eat yogurt every day and I sometimes make my own (using commercial yogurt as a starter), and I've never had a batch fail to start. Apparently I've only ever bought the live stuff.