When do I use .pxe, .kpxe, and .kkpxe?

[Sedorox]

from Etherboot.org:

• .pxe is an image designed to be chain loaded, unloading both the underlying PXE and UNDI code sections
• .kpxe is a PXE image that keeps UNDI loaded and unloads PXE
• .kkpxe is a PXE image that keeps PXE+UNDI loaded and return to PXE (instead of int 18h). From here
  

And there is also .kkkpxe - "The ipxelinux.0 build process should therefore now use undionly.kkkpxe instead of undionly.kkpxe."

Most often, you will want either .pxe, .kkpxe (for when you are using cached credentials, iirc), and .kkkpxe (usually the last two are in combination with pxelinux).

Typically I use .pxe here at home, and at work.