Move light sources while in Render Mode In one of the early tutorial, the presenter shows a rendered object but is able to move the light source illuminating the object so that the light on the object moves in real time and is still in rendered mode.  Could someone explain this.  Thanks in advance for any help.

I'm so new to this forum that I'm not sure how to reply to each of your answers.  Yes, both of you turned out to be correct and I thank you for your help.  I 'think' I upvoted the answers, but if I failed, I apologize.  If there is another way to replay in general, please let me know! Thanks again to both of you.
Presumably they were in Render Preview mode in the 3D View (Shift+Z) and moved the lamp from there by simply selecting the lamp in the outliner (since you can’t see it in render preview mode) or by some ither means and pressing G in the 3D View as usual to grab it and move it.