Vanilla kernel

http://en.wikipedia.org/wiki/Linux_kernel

Versions

Further developing his own code and integrating changes made by other programmers, Linus Torvalds keeps releasing new versions of the Linux kernel. These are called "vanilla" kernels, meaning they have not been further modified by anyone. Many Linux operating system vendors modify the kernels of their product, mainly in order to add support for drivers or features which have not officially been released as stable, while some distributions rely on vanilla kernels.

http://www.linuxquestions.org/questions/linux-general-1/what-is-vanilla-kernel-79388/

The kernels at www.kernel.ORG are vanilla kernels.

Each different distribution takes these vanilla kernels and adds their own type of flavoring. They may fix particular bugs in the code (Debian is very good at doing this), and they may add their own patches to do fancy things (SuSE adds a patch to do a boot screen animation), and they may add patches to enhance the facilities of the kernel (often using the source from the developmental branch of the kernel eg for very new USB devices).

Thus, although all kernels are derived from the same kernel source, not all kernels are equal.

So if you have a particular distribution and take advantage of some of the non standard features of the kernel, and then go and download a vanilla kernel, your hot new trendy USB device may no longer work and if you are on SusE you will no longer see a flashy boot time animation.