Known as the Mangala Charan Mantra
The term guru, relates to any venerable, or respected person. Most often used for a person who performs the purification ceremonies over a person and instructs them in the Vedas. However the author, Guru Arjan, called God his Guru.
This mantra was the first mantra Guru Arjun wrote when he started writing Sukhmani Sahib, the “Lagoon of the Peace”
There are many meanings to this. One which is incredibly beautiful, from the point of view of Guru Arjan Dev Ji is:
• Aad guray nameh - I bow down to the 1st Guru Sri Guru Nanak Dev Ji
• Jugaad guray nameh - I bow down to the 2nd Guru Sri Guru Angad Dev Ji
• Sat guray nameh - I bow down to my Satguru Sri Guru Ram Das Ji
• Sri gur dayvay nameh - I bow down to their (my satguru's) Guru Sri Guru Amar Das Ji
In this way Sri Guru Arjan Dev Ji pays respect to the four Guru Sahibs before them and seeks blessing to begin path of Sukhmani Sahib. This is an implied arth based on the perspective of 5th Guru. A more literal arth could be:
• Aad guray nameh - I pay respect to guru who has been guru since the start of time (aad meaning start)
• Jugaad guray nameh - I pay respect to guru who was present at the start of the yugs when creation began. Jugaad sach
• Sat guray nameh - I pay respect to the true guru Sri Guru Nanak Dev Ji
• Sri gur dayvay nameh - I pay respect to the guru who is true now and will always be the true guru Sri Guru Nanak Dev