This weekend, Sikhs around the world will celebrate Guru Nanak's birth.

Sikhism is a monotheistic religion that emerged around the turn of the 16th century in the Punjab region that today is divided between northern India and Pakistan.

Its founder, Nanak, regarded as the first Guru, or teacher, was born into a merchant-caste Hindu family in 1469. He worked as a shopkeeper until a prophetic epiphany prompted him to leave his home and family, and he spent the subsequent decades wandering the country and preaching.

At the time of Sikhism's founding, Hinduism and Islam pervaded the Punjab, and Sikhism bears hallmarks of both faiths, such as a belief in reincarnation similar to that of Hinduism and belief in a single god more akin to Islam. Sikhs, however, assert that their religion is not syncretic (i.e. created by the merger of two religions), but say it was rather a new idea that only appropriated elements of the existing belief systems.

According to Sikh tradition, Guru Nanak's first words following his revelation were, "There is no Hindu, there is no Muslim," and among the principle tenets of the faith is the conviction that anyone, regardless of caste (or gender), can become one with God.

Today there are an estimated 19 million to 25 million Sikhs, most of whom live in India's Punjab province.

They consider themselves disciples of the ten human Gurus (Sikh literally means "disciple" or "learner"), beginning with Guru Nanak and ending with Guru Gobind Singh, who died in 1708; thereafter they deem the Granth Sahib, a holy book containing devotional hymns as well as moral and spiritual guidelines, the current Guru and their supreme spiritual authority.