I am not very knowledgeable about the different groups that make up the Islam religion.

I do know that the largest groups are the Shia and Sunni. What I do not understand is the hatred that seems to divide them,

I can think of the same type of animosity between catholics and protestants which has also been very violent, Why do these groups, the sunni and shia, hate each other so much and does anyone see an end to the violence.