m in my previous reply  is a layer.
a simple example of layer or say a for example a 2D-Convolutional layer maybe:
import torch.nn as nn
layer=nn.Conv2d(in_channels=1,out_channels=32,kernel_size=3,stride=1)


torch.nn.Conv2D
I think that is too basic a question. Never mind but. You can check out Deep learning with pytorch Courses online.One such course