Provide a 2-3 sentence summary of the conflict between Saudi Arabia and Iran

The decades-old feud between them is exacerbated by religious differences. Historically Saudi Arabia, a monarchy and home to the birthplace of Islam, saw itself as the leader of the Muslim world. However this was challenged in 1979 by the Islamic revolution in Iran which created a new type of state in the region - a kind of revolutionary theocracy - that had an explicit goal of exporting this model beyond its own borders.