Why are there 'dot' in front of 'dsets' and 'model', but using 'util' in front of 'util' in training.py? [closed]

Folder structure: D:\master ├── p2ch11 │   ├── dsets.py │   ├── model.py │   └── training.py └── util └── util.py Command line: python -m p2ch11.training OK Questions: In the importing statements in master\p2ch11\t