There are times we think what Imam Mahdi (PBUH) is? What is a person like Imam Mahdi (PBUH) good for? What does he do and how does he do it? We do not understand!
If the Jewish people are seeking the arrival of Messiah Ben David, the Christians are seeking the same Messiah Ben David but its Christianized form who is Jesus Christ. Moslems, either Shia or Sunni, are seeking the arrival of Mahdi; and there is no disagreement between them on the fact that Mahdi (PBUH) is one of the descendants of Imam Ali (The first Imam of Shias) and her holiness Zahra (PBUH). There is something common in this concept.