Royal Jelly is to deposit HoneyFarm's native tokens, HONEY and BEAR, to earn 3rd party tokens such as BNB, BUSD, BTCB and so on.
In addition to that, HONEY holders can farm BEAR in advance of the layer 2 farming starts, which is amazing!
Royal Jelly is a fork of PancakeSwap's Syrup Pool.
You can find more details here.
There will be 3 kinds of Royal Jelly pools before the official start of layer 3 farming.