what is the meaning of "evaluation metrics, which depends on the dataset, e.g., "bbox",' ' "segm", "proposal" for COCO, and "mAP", "recall" for PASCAL VOC'"

[Alan-D-Chen]

In /Swin-Transformer-Object-Detection/tools/test.py,there is evaluation metrics, which depends on the dataset, e.g., "bbox",' ' "segm", "proposal" for COCO, and "mAP", "recall" for PASCAL VOC'. And I know that bbox is for object detection, segm is for instance segmentation, but what is the "proposal" for??