The booster nodes are a collection of nodes that, as the name cunningly suggests, boost values.
This node allows you to tweak the output of a material. The colour computed by the material can be boosted (multiplied) to enhance the effect.
Every material component has a Boost percentage setting (this is just a multiplier for the component).
If a scalar is connected to the respective Curve input, the Range parameter will be available as well.
This will use the values supplied by the Curve input to modify the final boost from the Boost value to the Maximum value.
If the Curve value is zero, Boost will be used, if the Curve value is 1, Maximum will be used. Other values will be interpolated.
Mathematically speaking: final = Boost + Curve * (Maximum - Boost)