There are many concepts of teachers in Islam. Islam is, in contrast to many westerners' understanding, an explicitly non-hierarchical spiritual community, but the concepts and names for spiritual teachers and secular functions are often mixed and confused. The Marja is a label used by the Shia community, meaning source to follow. Allamah is the most respected of the Marjas are entitled Allamah; this Persian name for Teacher is also used by some Sunnis to denote a teacher of extraordinary respect.