Scaling node handles instances size/scale.
Uniform scaling keeps objects proportions and scales instances for all axes equally.
Uniform scaling random gives random scaling in a specified range.
Uniform scaling by map scales instances depending on texture values. Range sets scale for texture black and white values.
Non uniform scaling allows to scale instances in every axis independently.
Scaling space sets what space (world, surface or object) to use for non uniform scaling.
Scale cutoff allows to remove too small instances in order to save computing resources.