There are several meanings and translations that can be inferred from the mantra, Sat-Tat-Aum. It can be taken to mean "The supreme absolute Truth” or “What is everlasting and unchanging is God.” More literally, it can be translated as “All that is.”
In Vedic spiritual teaching, the use of these three sacred syllables is considered integral to the pursuit of spirituality and truth. They are referenced in the yogic text, the Bhagavad Gita, by Lord Krishna, who teaches Arjuna that they are a highly effective tool to bring about purification and, ultimately, supreme spiritual awakening.
One use of Sat-Tat-Aum is as a mantra for salvation. Yogis believe that repeating the mantra has the potential to bring them closer to realization of God and unity, which can free them from the repeated cycles of death and rebirth.
Because there is no physical element to the mantra and it expresses spiritual concepts, it can be somewhat abstract and challenging to grasp. Therefore, some say that the mantra, Hari-Om-Tat-Sat, is a more accessible alternative because it begins with Hari, which denotes the physical form of God.