The term "Twelvers" refers to a branch of Shia Islam that believes in a line of twelve Imams as spiritual and political leaders. They hold that the twelfth Imam, known as Muhammad al-Mahdi, went into occultation in the 9th century and will return as the Mahdi, or guided one, to bring justice and peace. Twelvers emphasize the importance of the Quran and the teachings of the Imams, viewing them as essential for understanding faith and practice. This group is the largest sect within Shia Islam, primarily found in countries like Iran, Iraq, and Lebanon.