I didn't really see a good answer here, so I'll just explain.What's the difference between k9 and k11 exploits?
k9 is an arm9 exploit. This is what allows the fun stuff, like CFW, non-legit CIAs, emuNAND, and more. Technically, arm9 has a userland and kernel mode, but since arm9 userland has access to a syscall that literally "takes whatever code you pass in and executes it in kernel mode" (quoted from the 32c3 conference) taking over arm9 userland is enough to take over kernel9 (k9) and compromise the entire console.