recipe group name: what is it

It's a way to separate different recipes from your mod in the vanilla recipe book.

If you leave it to default, all your mod's recipes will be clumped into one 'square' of the recipe book.

Each group though, gets its own 'square' in the recipe book, whether set one recipe per group or a dozen, they each get their own square, which I think can be expanded by right-clicking.