Difference between [] and [[]] in numpy

Can anyone pleas tell what's difference between (if a is some numppy object, lets say:array) a[1] and a[[1]]. If I understand correctly I can edit 1 element of a with a[[1]], but not with a[1]...any other difference? Is it also something like that with [] I just view some element(s) and with [[]] I make copy? If it's to any importance I'm using python 3.