Hindus believe in GOD, who, in His highest form is known as the BRAHMAN, the Absolute, or the universal soul. He is within us and about us, transcending time and space. He is NIRGUNA, without shape and form, and without beginning or end.
The upanishads teach us that the whole universe is manifestation of the Brahman. Life in all forms has evolved from a single source of energy. It pervades all life and all things animate and inanimate. Since it is formless, Brahman is not considered as either male or female but it is referred by the impersonal pronoun “Tat” (meaning that). Brahman is also considered as “Satchidananda”. Sat is Truth. Chit is pure onsciousness and Chit is Ananda - pure happiness. All meditation begins with “OM Tat Sat”. It says that the ultimate reality, the Brahman, is the highest intelligence and is supreme happiness.
“OM” is considered as the sound symbol of Brahman. It is used at the beginning and also at the end of a prayer. It is said at all times whenever we think of Brahman.
Brahman is eternal, immutable, without a beginning or end. It is beyond senses, mind and speech, and so it cannot be described in words; it is said as the one where “the the eyes cannot reach, nor speech nor mind”, (Keno Upanishad: 1.3), or as “whence speech returns with the mind without reaching it (Taittiriya Upanishad: 11.9). Therefore, there is nothing positive can be predicated of Brahman. Even the Scriptures give but an indirect hint at IT. Utmost that can be said of IT is that “IT is Existence, Knowledge, and Bliss Infinite”. Even this is only by way of concession. The best description, however, of IT is, “Not this , not this”, that is rejecting from IT everything which is limited by the senses and the mind function and reasons, one is within the sphere of relativity, but when stops functioning and is annihilated, then one attains Samadhi and realizes Brahman.
When one tries to express this Absolute (IT), in terms of thought and speech, IT ceases to be Absolute and becomes phenomenal. As such the descriptions given by different persons are likely to differ according to the standpoint or plane of consciousness from which they describe the Reality. All these descriptions of the one Reality may differ among themselves; it is like the photographs of the sun taken from different distances by one, are the photographs of the same sun and yet they would vary from one another. When a person describes the Absolute from the material plane, - when he is conscious of the body, -- God, Soul, and Nature, appear as three different entities, God being the ruler of the two. When he sees IT from the mental plane – when one is conscious of himself as a jiva – he sees the three entities as one organic unity, and realizes himself as part of GOD. But when one rises to the spiritual plane and is conscious of him as the spirit, then he realizes that he and the Absolute are one. To start with, GOD appears as extra – cosmic being; then he is seen as the GOD immanent in the Universe as its inner ruler; and finally one ends by identifying the soul with GOD.