What is different between train=False and train=True

what is different between the data in training.pt and test.pt ?
does mean that (train=True) download a dataset been trained by default , and (train=False) a un trained dataset ?

trainset = datasets.FashionMNIST("~/.pytorch/F_MNIST_data",download=True , train=True , transform=transform)

testset = datasets.FashionMNIST("~/.pytorch/F_MNIST_data" , download=True , train=False, transform=transform)


The split of the data is different i.e. not the same data is loaded as explained in the docs