The national flag of Bahrain (Arabic: علم البحرين) consists of a white band on the left, separated from a red area on the right by five triangles that serve as a serrated line.
It is very similar to the flag of Qatar, which has more points and has a darker red.
Red is the traditional colour for flags of the Arab states of the Persian Gulf. The white is on the hoist side; the five points represent the five pillars of Islam.
The flag originally had twenty-eight white points, but this was reduced to eight in 1972. In 2002 the number was again reduced to five, so that each of the points could stand for one of the Five Pillars of Islam
The oldest known flags of Bahrain were plain red. In 1820, Bahrain signed a treaty with the United Kingdom, and a white stripe was added to the flag to indicate the truce. In 1932, a serrated edge was added to distinguish the flag of Bahrain from those of its neighbours. Wikipedia