In the Preferences Dialog will you set nearly all adjustable values in The GIMP, some additional preferences values are still only available in the gimprc file in your personal GIMP directory. For further information of such values consult your system wide gimprc file usually located in /usr/local/etc/gimp/1.2.
There are several categories that you can adjust. New File which controls the default values of when you create a new file and the comment which is attached to new images by default. Display which controls transparency type and and 8-Bit display settings. Interface which controls preview, navigation, help, image window, and tool options. Environment which controls memory usage, file saving and scaling. Session which controls the session management in GIMP. Monitor which lets configure your monitor resolution. Directories which controls where GIMP loads additional resources such as plug-ins, scripts, patterns are located. It also controls where GIMP's swap file is located. The swap file location is very important for GIMP's performance.