A kernel-image is a pre-compiled kernel; it\'s the base, the core, of
 Debian GNU/Linux (and other Linux-based operating systems).
 
 This is in contrast to a kernel source tarball (a .tar.bz2, as you
 mention above), which must be configured and compiled. The source is
 what the programmers write. Then they (or you) compile it into a binary
 image.
 
 Installing a kernel-image is usually much easier than "rolling your
 own". Of course, compiling your own kernel has its advantages, such as
 being customized to your hardware rather than being more generic, etc.