Simply all the kernel that downloaded from the
http://kernel.org/ are "
Vanilla Kernel".
We know that the home site of the linux kernel is at
http://kernel.org/. All the linux distributions will use the stable linux kernel from here(of different kernle versions[for ex: 2.6.32.46, 2.6.35.14 etc]).
Here comes the difference, so some distributions will patch the kernel before use it in its distribution. For example
SUSE's kernel patch for boot screen animation,
Debian's kernel patch for LOGO , bad-ram. [
Page to debian's kernel patches ].
Now consider the security patches like
SElinux,
grsecurity. The team that works on these projects are not able to know, monitor & follow back the kernel patch by different linux distributions. So, they do write patches only to the kernel in
http://kernel.org/.
So, its true that the kernel you are using may not be completely same as the
Vanilla kernel, even if they are same kernel versions. Some features/securites that patched in one distribution and may not be patched in another. So if one want a
Plain kernel he should go with
vanilla kernel download only from
http://kernel.org/ not from their distribution's repository.