2.  Starting GIMP the first time

The first time you run GIMP, it goes through a series of steps to set up options and directories. This process creates a subdirectory of your home directory called .gimp-2.4. All of the information about the choices you make here goes into that directory. If you later remove that directory, or rename it as something like .gimp-2.4.bak, then the next time you start GIMP, it will go through the whole setup sequence again, creating a new .gimp-2.4 directory. You can exploit this if you want to explore the effect of different choices without destroying your existing installation, or if you have screwed things up so badly that your existing installation needs to be nuked.