When you save a schematic as a `Module`, you can then select it from: `Parts > My Modules` and then place it into any schematic sheet. For example if you have a schematic for a 5V regulator that you use in many different circuits, instead of having to copy and paste it from one schematic to the next and then edit the netlabels each time you paste it, you can just place the schematic `Module` into the destination schematic. PCB modules work in a similar way but for the component placement and tracking in a PCB. * Please note that when you save a schematic as a `Module` you cannot then directly convert it to a PCB: you must place the module into a schematic and then save it as a `Schematic` first.