Particles Frac Delta has little explanation

[ghost]

It is not understood what is the function of activating or deactivating it: https://github.com/godotengine/godot-docs/blob/b6cb5c3ee7ec86b8730bb14af80c4a4089328175/tutorials/2d/particle_systems_2d.rst#L126

[BornStellarMakesEternalLasting]

I too don't know what the term frac delta is supposed to mean. I agree that there really isn't a good description of what it is in the docs.