For tens of thousands of dispossessed and displaced Palestinians, Hamas is a resistance movement incorruptible and invulnerable in the fight against Israeli occupation.
For Israel and most Western nations though, Hamas is a terrorist organization that has orchestrated a cold-blooded campaign of suicide bombings in the region.
Where most Westerners see enraged fighters willing to die for the cause rather than compromise, many Palestinians view Hamas as a disciplined group that provides education, housing, medical facilities and, most importantly, a sense of pride and defiance in the face of decades of humiliation and defeat.
Observers say the grass-roots organization could make or break any hopes for peace in the Middle East. Here are some frequently asked questions about the group.
What is Hamas?
Hamas is the Arabic acronym for the Islamic Resistance Movement, which began operating in early 1988 after the start of the 1987 uprising -- also known as the first Palestinian intifada.
How and when was Hamas founded?
In 1987, soon after the outbreak of the first Palestinian intifada, Sheik Ahmed Yassin emerged from the ranks of the Egyptian-based Muslim Brotherhood to found Hamas.
Born in 1938 in what was then British-ruled Palestine and educated at Egypt's al-Azhar University -- the birthplace of the Muslim Brotherhood -- Yassin formed the belief that Palestine was an Islamic land and no Arab leader had the right to give up any part of Arab lands. It was to become the central tenet of Hamas, the largest Palestinian militant Islamist organization.
Who leads Hamas?
Yassin served as the group's spiritual leader until his assassination on March 22, 2004, by an Israeli missile strike. Following his death, Abdel Aziz Rantisi, a firebrand leader and well-known Hamas spokesman, took over the organization's leadership. But three weeks after Yassin's assassination, Rantisi was also killed by an Israeli missile.
As tens of thousands of supporters took to the streets in Gaza vowing revenge, Hamas appointed a new leader, whose identity was kept secret due to security reasons. One of Hamas' major military leaders, Khalid Meshaal, currently lives in Syria following a bungled Israeli assassination attempt in 1997. Meshaal is believed to head the Hamas exile wing.
What are the goals and ideology of the group?
Like the Muslim Brotherhood, Hamas believes in the revival of strict Islamic values in government and society. The official Hamas rhetoric is opposed to the very existence of the Israeli state.
How does Hamas operate?
A widely popular grass-roots organization, Hamas has a socio-political wing and a military wing. Although the exact number of active members is not known, the group has tens of thousands of supporters and sympathizers.
The socio-political wing operates a number of schools and hospitals in the West Bank and Gaza, providing services in the refugee camps from which it draws its support base.
The military wing is named the Izzedine al Qassam Brigades after the Palestinian leader who fought the British occupiers of Palestine in the 1930s. While it initially drew its cadre of fighters from the Muslim Brotherhood, it has grown into a formidable organization, capable of carrying out bloody terror attacks, notably suicide bombings, in Israel.
Who finances Hamas?
It's a difficult question. Hamas is believed to receive funding from Palestinian expatriates, the Iranian government, and private donors in Saudi Arabia and other Arab states.
Charities in the United States, Canada and Western Europe have funded Hamas-linked social service groups. In addition, several individuals in the United States have been charged with providing material support to the organization.
Where does Hamas stand in the Palestinian power structure?
Hamas is essentially in opposition to the Palestinian Authority, although the late Palestinian leader Yasser Arafat was careful not to antagonize Hamas fearing the wrath of the organization's tens of thousands of supporters and sympathizers.
In the past, the Palestinian Authority has launched major offensives against the group, notably the arrests of nearly 1,000 Hamas supporters and the taking over of mosques in Gaza in 1996. But the Palestinian Authority has had to be careful not to drive Hamas underground and has made some attempts to co-opt the organization into mainstream Palestinian politics.
Why is Hamas popular?
Hamas is seen as an honest organization compared with the Palestinian Authority, which had a reputation for corruption -- especially during the brief period of relative peace after the Oslo Accords were signed in the mid-1990s.
The group's policy of opposing short-term agreements with Israel until there is a complete Israeli withdrawal from the Palestinian territories won many supporters after Oslo, when Israeli Prime Minister Ehud Barak implemented a massive expansion of Jewish settlements in the territories.
Hamas' popularity again soared during the second Palestinian intifada, which began in September 2000.