Sulfate indicates the carrier molecule that the magnesium is bonded to. Magnesium can be bonded to other carrier molecules as well such as magnesium citrate, magnesium chloride, etc. Magnesium chloride or magnesium citrate may two of the better ways to get magnesium to cross the gut membrane into the blood so it can be utilized systemically. Magnesium sulfate tends to remain in the gut with much less crossover.