You are working on a classification problem and applying softmax layer to the output which will emit the probability for all classes.
Here, you are predicting a particular class (i.e. a class which has max probability predicted by your network)
Ground truth is actual label for current image and pred is your predicted class.
pred is tensor of size [ batch_size x 1 ] similar to ground truth tensor.
I would recommend to read up on classification problems here for learning: https://pytorch.org/tutorials/beginner/blitz/cifar10_tutorial.html