Took me a while to find out... Looks like prisms is a suggested lightning Standard to do lightning payment splits natively in lightning. Bolt-12 is the official name.

At the moment we can do split zap payments in some nostr clients but it's done on client side, multiple lightning payments are sent out according to the split definition.

In the future we will be able to leverage bolt-12 (prisms). This will send a single lightning payment to the recipient and the recipient will forward payments according to the bolt-12 definition.