Why it matters.
Choose where and when the camera should look for sharpness.
A closer look.
Focus mode determines how focusing behaves over time. AF-area mode determines which part of the frame is considered. These are separate decisions.
Choose a single focus area over a stationary object. Then compare a broader automatic area.
Keep in mind.
Low contrast, poor light, repeating patterns and obstructions can make autofocus unreliable.