
Hinduism is not just a Religion, it is a way of Life, Belief and Attitude.

Hinduism is the "oldest religion" in the world, and many scholars and practitioners refer to Hinduism as Sanātana Dharma, "the eternal law" or the "eternal way" beyond human origins. It prescribes the "eternal" duties all Hindus have to follow, regardless of class, caste, or sect, such as honesty, purity, and self-restraint.
Adhi Shankarar 788 AD - 820 AD
He was the first person to name the 6 religions under Sanathana dharma which until then, for nearly 6000 years, was a Vedic traditional way of life.
Shaivam (Shiva or non-duality Philosophy)
Vaishnavam (Vishnu or duality Philosophy)
Shaktham (Shakthi or Universal Mother)
Ganapathiyam (Ganesh – Lord Ganapathi)
Kaumaram (Skanda - Lord Muruga)
Sauram (SUN – Lord Surya)
One contradiction with in Sanatana Dharma is Advaita and Dvaita Vedanta ( non-duality and duality philosophies). Both philosophies are based on Para Brahma or Param Athma the supreme or ultimate reality.
But the difference is followers of Advaita, believe Param Athma and Jiva Athma (individual soul) are all of the same essence. Whereas, followers of Dvaita believe Param Athma and Jiva Athma are different and difference is real. Followers of Dvaita further believe each and every Jiva athma (individual soul) are different and unequal, which is preposterous to followers of Advaita.

The single word AUM (ॐ) (or OM) is known as the pranava mantra (प्रणव मंत्र) and is perhaps the most significant mantra in hinduism. It is known as the primary (or seed) or pranava mantra (or bija mantra) because it contains the seed for all other mantras within itself. प्रणवो धनु: शरो ह्यात्मा ब्रह्म तल्लक्ष्यमुच्यते । अप्रमत्तेन वेद्धव्यं शरवत्तन्मय ो भवेत् ।।

Aum Bhur Bhuvah Swah, Tat Savitur Varenyam Bhargo Devasya Dhimahi, Dhiyo Yo Nah Prachodayat ॐ भूर्भुव: स्व: तत्सवितुर्वरेण्यं । भर्गो देवस्य धीमहि, धीयो यो न: प्रचोदयात् ।।

BRAHMA (Creator) - VISHNU (Preserver) - SHIVA (Destroyer) (Hari Om) | Gurur Brahma | Gurur Vishnu | Gurur devo Maheshwarah | Gurur saakshaat para-brahma | Tasmai Shri Gurave namah || The Guru is Brahma (the God of creation) | The Guru is Vishnu (the God of sustenance) | The Guru is Shiva (the God of annihilation). He creates, sustains knowledge and destroys the weeds of ignorance. | I salute such a Guru ||