Modifier kit is a collection of shapes for Blender created with modifiers. If you go to the properties / modifiers panel, you will see how settings can change drasticaly the shape of a basic object ( cube, sphere, cone, cylinder or donut ). You can use it to learn modifiers, for inspiration, add sci-fi / architectural details or logo creation or whatever you like. 

The modifiers setups are easy to tweak, to make endless variations...

The Modifier Kit is delivered with a simple addon "Copy modifier " as bonus. With it, you can apply Scale and copy modifiers settings of an object to an other in one click.