Kritadokument(*.kra) and Krita Brush Preset(*.kpp)

What a difference there is Kritadokument(.kra) and Krita Brush Preset(.kpp)

.kra stores your artwork in a form that can be saved and loaded - so you can keep your layers with correct modes, text possible to edit, and so on. It’s the equivalent of gimp’s .xcf or photoshop’s .psd. Those working formats can be then exported to .png or .jpg file that is a compressed image, ready to store, and upload on the internet
.kpp is a format to store the settings of one particular brush. It contains its icon, and all of the settings. Each brush you can pick in the docker on bottom-right is in fact a .kpp file that krita reads on start (to be correct, those .kpp files are grouped in one .bundle file to make it easier to move and inactivate them)

thank you very much