It is the same thing. Don't worry about that :). It is MgSO4∑7H2O, (magnesium sulfate).
Somebody sells it in little bottles as laxative and charges too much.
I have been using it ( I am sure most of us here) the regular/bath one for years, during my liver flushes.
But if you want the one labeled as laxative, go for it. Epsom Salt is not that expensive anyway. :)