Mohammad Reza Shah Pahlavi became the Shah of Iran in 1941 when the British after an Anglo-Soviet invasion forced the abdication of his father Reza Shah. The Pahlavi dynasty was the ruling house of Iran from 1925 until 1979. During this time Iran begun a massive modernization process and huge improvements were done in the fields of health care, education, law & order, industry etc.

Khomeini was a cleric and opponent of the Shah. He was critical of the Shahs policy of modernization and secularization. He objected loudly when the Shah granted women more freedom in the 1960s. He was exiled to Iraq but later went to France where he spoke of revolt against the Shah. Most of the protesters against the Shah were the Islamists and the Communists. After the revolution, Khomeini became the leader and established an "Islamic Republic".

Ahmadinejad was one of the presidents and Mousavi also participated in the elections at that time. It is important to know that all candidates for the elections have to be approved beforehand, which is not a truly democratic system. Mousavi was part of Khomeinis inner circle and he was also the Prime Minister of Iran from 1981 and 1989 , during a time where thousands and thousands of political prisoners were executed.

Shah means king. The Shah was the second and last king of the Pahlavi dynasty in Iran, which had been an absolute monarchy until then, with two notable efforts by the Iranian people to subject the shshs to Constitutional limits, once in the Cinsititional Revolution of 1907- ~ 1909, and later during the Mossadegh premiership up to 1953. Both efforts were frustrated by foreign colonial powers, who reinstalled the shah whenever he was ousted.

Ayatullah Khomeini was a high ranking cleric and opponent of the Shah and a critic of his US ties. He was exiled to Baghdad, then he left for Paris, where he and his supporters and hangers-on agitated for the fall of the shah, which happened in1979.

Ahmadinejad wad simply one of the latest Irsnian presidents who served his two terms, caused son controversy, son of it legit but much of it not.

Mousavi was has opponent in his last election term. And Moussvi lost, so he claimed fraud, but wsd never able to back it up. The media in the US who have long expected the regime to fall, as well ad embittered exiles, tried to portray Moussvi as a dissident but in fact he is very much a regime insider, a former high official, and loyal to the Islsmic Republics basic tenet of clerical rule.

Be careful of just getting one side of highly debated and polarized issues regarding Iran.