Sure, this is the doc’s 1.
What sequential do is to gather  a serias of layers into one so you can call all the layers upon execution.
for example:
conv_module = nn.Sequential(
          nn.Conv2d(1,20,5),
          nn.ReLU(),
          nn.Conv2d(20,64,5),
          nn.ReLU()
        )

So now if you can  conv_module(someTensor) you will get as out the tensor processed via all the layers inside the sequential.