Hi, i have a question, because i’m new in DNN, so i read term about  transfer learning, there are stragtegies to do a transfer learning, like we freeze our base net layer or just classification layer, i want to know if there are simple explanation behind this (would appreciate with math explanation), what happend to the frozen layer while training?
i read github code to freeze some layer like this:
def freeze_net_layers(net):
    for param in net.parameters():
        param.requires_grad = False

what is requres_grad? what happen if we set the value true?