What is the fundamental Problem of Evil?

The fundamental heart of the Problem of Evil is the apparent inconsistency between how we see God and the existence of evil and suffering in the world.

God is seen as omni-benevolent, all-loving, and as omni-potent, all-powerful. The fact that evil exists means that either God is not willing to save us from evil - he is not omni-benevolent - or he is not able to save us from evil - he is not omni-potent. This problem is known as the Inconsistent Triad.

Either interpretation is not consistent with the traditional view of God, and so theories have to be formed to defend God in the face of this problem. These theories are known as theodicies.