Not All Responses Are Created Equal
You set cruise control to 65 mph. What happens next matters.
Sluggish system: Takes 30 seconds to slowly reach 65 mph
Aggressive system: Shoots to 72 mph, drops to 60, oscillates for 10 seconds, settles at 65
Well-tuned system: Smoothly reaches 65 mph in 5 seconds with minimal overshoot
All three eventually reach 65 mph, but the journey is wildly different. That journey is called the system's response.