As you know, ZBrush includes a tool called ZModeler for low poly and box modeling. But its interface is very different from what is usual: it's all text. Power Modeler is a ZBrush plugin that adds 30 buttons with icons. With it, you can use ZModeler in a much more powerful, easy, fast, and visual way. With Power Modeler you can use ZModeler in the same way as other 3D low poly modeling apps work: clicking on icons. If you already use ZModeler, it will speed up your workflow and help you save time and work in a more visual and comfortable way. If you don't, and you come from other 3D applications, it makes easier for you to adapt to ZModeler and start using it.