The Waheguru Mantra is the most popular Sikh mantras. The Wahe Guru or Vaheguru Mantra is also called the Guru Mantra sung by Destination Sikh Wedding Priest Freedom and Leela. It is one of the many Gurbani mantra Shabads they sing at Destination Anand Karaj.
The formal Sikh and Khalsa greeting is ‘Waheguru Ji Ka Khalsa, Waheguru Ji Ki Fateh”.
Waheguru – Wah (Great) Guru (remover of darkness). Great is the remover of darkness.
Bhai Gurdas, the first writer of Sikh scriptures (Adi Guru Granth Sahib), explains in his writings the definition of the word VaHeGuRu:
“Va” stands for Vishnu
“He” for Hari
“Gu” for Gobind
“Ru” for Ram.
The combination of these 4 sounds are used in reference to the Creator “Va Hey Gu Ru”.
Waheguru in Wikipedia