What does resting mean I'm a little confused with what resting actually means.

I've typically seen this term being used where you move food (typically meat) from the oven/grill/heat and then keep it warm for "some time" (maybe 10's of minutes depending on the size).

What has confused me is Gordon Ramsay's burger video, where he is cooking burgers on a BBQ. He then moves the burgers to the "resting" rack (if that is the right term) within the BBQ. This rack is still above the heat. To me, this is not resting, this is cooking at a lower heat. 

https://youtu.be/v191Y8AUk6w - He says this at 4:43 where also says "they'll continue cooking". AT 5:50, he closes the lid!

I'm assuming resting does not mean "left alone" because many recipes, such as a roast, call for us to put meat in the oven and leave it alone until cooked.

So my question, which may be a double question is: Is there a definition of what resting means and if so, what is it?
There is, as you've seen, no universally precise definition. Broadly, though, "resting" refers to allowing heat to diffuse through the food. Although the burgers are "still cooking" once placed on the higher rack, the amount of heat being applied is nowhere near as high as when they were on the grill, and following the resting the temperature differential will be lower than when they were first taken off the grill.