From food cooking over a campfire to some obnoxiously expensive gas grill, they've all got a personality. It's the way they distribute heat. Hot spots, cool spots, the weird way piling up the coals on the left makes that one spot on the right hotter. Coal grills are probably much more consistent – there's heat where you put the coals. Gas grills, you gotta pay for that convenience of the knob. My last grill I had for >10 years, and over time learned that the back was always WAY hotter than the front and that one spot over there was just cold. And by "learned," what I really mean is ruined food all sorts of ways.
With a new grill in the backyard and the carnapocalypse coming tomorrow I wanted to get a better feel for my grill without squandering 20+ steaks. A quick trip to the grocery and one loaf of sliced white bread later, I've got some interesting insights.
I pre-heated the grill on full high for ~10 minutes. Put down slices of bread covering most of the grill. Grilled them for 45 seconds, then pulled them all off in the order I put them on. You can see above just how variable the grill is, with some insane hot spots, and other parts where the bread is basically untouched. There's clearly a spot over on the right middle that's just punishingly hot - >900 degrees is my guess. Going to try turning the grill down over there and seeing if it mellows out.
Each spot on your grill might be a bit different. Try it out, and get a feel for what's going on.