Extended Input Devices
When enabled, the same tool and tool options will be used for all input devices. No tool switching will occur when the input device changes.
This large button allows you to set the devices associated with your computer: tablet, MIDI keyboard, etc. If you have a tablet, you will see a dialog like this:
When you check this box, GIMP remembers the tool, color, pattern, and brush you were using the last time you quit.
Self-explanatory.
Delete your settings and restore default settings.