Complex sentence: In the brane picture, the other three forces (electromagnetism and the weak and strong nuclear forces) are localized on the brane, but gravity has no such constraint and so much of its attractive power "leaks" into the bulk.
Split into simpler sentences: In the brane picture, the other three forces (electromagnetism and the weak and strong nuclear forces) are localized on the brane, but gravity has no such constraint. Much of its attractive power "leaks" into the bulk.