If the IoU threshold becomes stricter, fewer predicted boxes may be counted as true positives.

IoU measures the overlap between the predicted bounding box and the ground-truth bounding box.

mAP is the same thing as accuracy, so it only measures the proportion of correct predictions.

AP summarises the precision–recall performance of a detector, rather than just checking one fixed confidence threshold.

Confidence score helps decide whether a predicted bounding box is kept or reported by the model.

A prediction with high confidence is always counted as a true positive, even if the predicted box does not overlap well with the ground-truth box.