it tells you wich kernel configuration flavour it has. The PAE version tells you that on this version, the PAE option is activated (Physical Address Extension, enables support of more than 4Go of RAM on 32bits systems) and XEN tells you that the XEN virtualization is activated.
Try to build your own kernel and read the documentation shipped with it, using the menuconfig (make menuconfig) to configure the kernel can teach you a lot of things on it.
PS: I forgot to tell about the smp option : Symmetric Multi Processing : Enables multi CPU/core support.
Last edited by antegallya; 09-13-2009 at 05:03 AM.
Reason: add smp