"Sikhs (/siːk/ or /sɪk/; Punjabi: ਸਿੱਖ, sikkh, [sɪkkʰ]) are people associated with Sikhism, a monotheistic religion that originated in the 15th century in the Punjab region of the Indian subcontinent, based on the revelation of Guru Nanak. The term Sikh has its origin in the word śiṣya (शिष्य), meaning 'disciple' or 'student'.

Male Sikhs generally have Singh ('lion') as their middle or last name, though not all Singhs are necessarily Sikhs; likewise, female Sikhs have Kaur ('princess') as their middle or last name. Sikhs who have undergone the Khanḍe-kī-Pahul ('baptism by Khanda') which is an initiation ceremony known as Amrit are from the day of their initiation known as Khalsa Amritdhari Sikhs, and they must at all times have on their bodies five Ks:

kesh, uncut hair, which is kept covered usually by a dastār, also known as a turban;
kara, an iron or steel bracelet;
kirpan, a dagger-like sword tucked into a gatra strap or a kamal kasar belt;
kachera, a cotton undergarment; and
kanga, a small wooden comb.

According to Article I of the Sikh Rehat Maryada ('code of conduct'), a Sikh is: Any human being who faithfully believes in One Immortal Being; eleven gurus, from Guru Nanak to Guru Granth Sahib; the teachings of the 6 Gurus, 15 bhagats, 11 bhatts, 4 Gursikhs and the baptism bequeathed by the tenth Guru."

          (from Wikipedia)

     A Brief Introduction to Sikhism

     Guru Granth Sahib - Sacred Scripture of the Sikhs (compiled by Gurmit Singh)