[plug] debian patches to kernel source?

[Daniel]

Hello All,
I'm befuddled by this:
apt-cache search kernel-source
... snip ....
kernel-source-2.4.21 - Linux kernel source for version 2.4.21 with
Debian patches
kernel-source-2.5.69 - Linux kernel source for version 2.5.69 with
Debian patches
------------------------------
I thought debian used a raw source kernel - what are these Debian
patches for the kernel?

I look forward to your responses.

Thanks,
Daniel.