I hear the terms shikantaza and "silent illumination" used by different sources and am not quite clear on the distinction. Shikantaza (????) literally means "just sitting" and my understanding is that it is done without any conscious striving towards a goal. But if we sit down to practice something called "silent illumination" (???), this seems to imply a purpose or desired result -- that is, the result of being illuminated.

What is the relationship between the two? And how does either practice tie in with the calming/insight (samatha/vipassana) combo found in earlier Buddhism?