Salman 108
that's the thing you never can find out for ever ! i means Velaiat , it is a big fact that i can't just explain to you in this forum because i need to talk pages about it ......
but as a short explanation : Allah gave prophets and Imams (not khalifa!) a lengthal velaiat , it means that because of their rank of being a Perfect human god gave them different duties and power . If Allah wants he could just remove the Velaiat of them but now they have it , and because we know that they have that velaiat , and that they (+allah and angels) can see us and hear us , we kind of tell them our need and if they ask god (not like simple asking it is hard to tell) , allah mostly accept it because of their ranks ........
and that exists if you want it or not ! and that's difference between the theory of shia and sunni !