The difference between i, batch and step

What do i, batch, and step represent? what differences are there?

for i, batch in enumerate(dataloader):
        real_A = Variable(batch["A"].type(Tensor))
        real_B = Variable(batch["B"].type(Tensor))
for step, (x, y) in enumerate(data_loader):
            images = make_variable(x)
            labels = make_variable(y.squeeze_())

i and step represent the same variable returned by enumerate (the counter of the current loop).
The return value of the dataloader seems to be a dict in the first example, so batch will contain the keys 'A' and 'B', while data_loader will return a tuple which is unpacked to x and y.

In Example 1, A and B respectively represent two image data sets. So does batch here refer to batches of images?Is batch and batchsize related here?
In Example 2, ImageFolder is used. Do x and y refer to the images in the folder and the folder name under the path?

Your code snippets just show the usage of the return value of the DataLoaders.
I assume that no custom collate functions etc. were used, but the “standard” approach of creating a Dataset and wrapping it into a DataLoader.

batch is the name of the returned variable from the DataLoader. Based on the following lines of code, it seems that it’s a dict containing batches of 'A' and 'B', which both seem to be tensors.

A batch contains batch_size number of samples.

ImageFolder will return the loaded image and the corresponding target, not the folder name.
The subfolders will be sorted and ImageFolder will assign a class index to each folder.

Thank you very much for your answers!