About mean and std

When we prepare data, we need to normalize the data like this:

if transforms is None:
normalize = T.Normalize(mean = [0.485, 0.456, 0.406],
std = [0.229, 0.224, 0.225])

Is the mean and std value here the mean and std of the training data on my own data set?
If so, what is the simple way to get the mean&std in pytorch?

the mean and std is relate to which model you use

Can you give some examples?