The terms guru and acharya refer to a teacher or master of a tradition. The basic meaning is of a teacher who teaches through example and conveys knowledge and wisdom to his disciples. The disciple in turn might become a teacher and so the lineage continues through the generations. One story that captures the spirit of the teacher is that a mother asks the teacher to stop her son eating sugar for he eats too much of it. The master tells her to come back in a week. She returns and he tells the child to do as his mother says and the child obeys. Asked by the mother why he delayed for a week, he replied 'a week ago I had not stopped eating sugar!'
Gurus are generally very highly revered and can become the focus of devotion (bhakti) in some traditions. A fundamentally important teaching is that spiritual understanding is conveyed from teacher to disciple through a lineage and when one guru passes away he or she is usually replaced by a successor. One guru could have more than one successor which leads to a multiplication of traditions.