The accursed leveling problem is present in many personal 3D printers. Before you can use your printer, you must ensure that the print head is synchronized with the print bed so that the plastic extrusion lands correctly. Since the print head usually cannot be adjusted, the synchronization is done by "leveling the bed".
The process of leveling is sometimes tricky and difficult, depending on your device, but PP3DP is making it a bit easier with their new calibration software. The software provides an easy to use control window that can quickly level the bed.