What is the difference between using backbone architecture and transfer learning?

hi im super new to this field(deep learning, computer vision) so this question may sound dumb. In this link (https://github.com/GeorgeSeif/Semantic-Segmentation-Suite), there are pre-trained models (eg, ResNet101) called front end models. And they are used for Feature Extractor. I found these models are called backbone models/architectures generally. And the link says some of main models(eg. DeepLabV3,…