TABO TABO DHARI PRAPHU VIVIDHASHARIA,
HARAHINATH SAJJAN KAI PIRA ||

From the above citings it is clear that God takes incarnation for very special; reason only. That is, it has some special purpose. When all the incarnations (Avataras) and forms have special purpose of their own, it is not necessary then to clarify all of these reasons. It can be understood with one-or two examples alone, such as Narashima Avatara. To preserve the sanctity of Brahmas boon, God had to appear in form of half lion and half human in order to protect the life of Prahlad. Similarily, to free the earth from the terror of the demon king Ravana, Lord Shiva and Lord Vishnu had to appear as monkey (Hanumana) and human (Rama) forms respectively, Because Ravana had asked for the boon.

Meaning : Except the human being and the monkey, nobody else could kill me.

From these two examples, it becomes clear that God, appears in different forms (incarnations) on earth in order to run the universe in religious way and protect their devotees and establish the rule of religion. Lord Rama, Lord Krishna, Hanumana, Ganesh, Durga, Laxmi, Saraswti, Parvati etc. are different appearances of God.

For the fulfillment of desires there are direction for worship of various gods and goddesses. All these will be described in the Karma-Kanda section. Suffice it would be here to say that faithfully worshipping the gods desired results can be got!

JANAMI DHARMAM NA CHA ME PRAVRITIH |
JANABHYADHARMAM NA CHE ME NIVRITIH ||
Meaning : I know the religion, but am not inclined towards it. I also know their religon, but I can not get rid of it either. MONOTHEISM : THERE IS ONLY ONE GOD

God is one but his forms are many. As per this principle, all the gods are present in the form of Ganesha. Scriptures even say that in a single idol you can worship your tutelary God. It means to say that if you have an idol of Ganesha, you can worship in it Vishnu, Shiva etc, or any other god of your desire, the main thing is the feeling of Devotion. In Ganesh Purana is written :

SHAIVESTVADIYAIRUT VAISHNAVAISHCH,
SHAKTAISHCHSAVRAIRAPI SARVA KARYE |
SHUBHASHUBHE LAUKIKAVAIDIKE CHA,
TVAMARCHANIYAH PRATHAMAM PRAYATNATA ||

Meaning : After killing of Tripura Lord Shiva said ; O Ganapati, people of all the sects - Shaiva, Vaishnava and Shakta will worship you first in their all worldly or non-worldly, auspicious and inauspicious deeds.

From this evidence it is certain that the scriptures assume the Paramatma, who has no beginning, no end; who is formless, but who has created the world and who is the raiser and destroyer of the world, as Ganesha is the base of everything. Hence in the beginning of every task He is worshipped first of all.

EKAM SAD VIPRAHBAHUDHA VAPANTI

Meaning : The knowledgeous people explain the single, almighty Paramatma in many different ways. Such as by the token of various relations and places, a single man becomes father, son, uncle etc. and at other place he becomes singer, warrior, guardian etc. and comes to be addressed with various nouns, still he is the single and same person. Similarily, inspired by their feeling people call the same God by different names. This is the spirit of Ekeshwaravada or Monotheism.

The OM Symbol

"The goal which all the Vedas declare, which all austerities aim at, and which men desire when they lead the life of continence . is OM. This syllable OM is indeed Brahman. Whosoever knows this syllable obtains all that he desires. This is the best support; this is the highest support. Whosoever knows this support is adored in the world of Brahma."
~ Katha Upanishad I~ 

The Om (or Aum) sign is the main symbol of Hinduism.
Most religions indicate that creation began with sound-- In the beginning was the word...
For the Hindus & Buddhists, Om is the primordial sound, the first breath of creation, the vibration that ensures existence. Om sign signifies God, Creation, & the One-ness of all creation.

The Om symbol is a sacred syllable representing Brahman, the impersonal Absolute - omnipotent, omnipresent, and the source of all manifest existence. Brahman, in itself, is incomprehensible; so a symbol becomes mandatory to help us realize the Unknowable.  Om, therefore, represents both the unmanifest (nirguna) and manifest (saguna) aspects of God. That is why it is called Pranava, to mean that it pervades life and runs through our prana or breath.

Aum is said to be the essence of all mantras, the highest of all matras or divine word (shabda), brahman (ultimate reality) itself. Aum is said to be the essence of the Vedas.

By sound and form, AUM symbolizes the infinite Brahman (ultimate reality) and the entire universe.

A stands for Creation

U stands for Preservation

M stands for Destruction or dissolution

This is representative of the Trinity of God in Hindu dharma (Brahma, Vishnu and Shiva)

The three portions of AUM relate to the states of waking, dream and deep sleep and the three gunas (rajas, satva, tamas)

The three letters also indicates three planes of existence, heaven (swarga), earth (martya) and netherworld (patala)

All the words produced by the human vocal organ can be represented by AUM. A is produced by the throat, U & M by the lips

In the Vedas, AUM is the sound of the Sun, the sound of Light. It is the sound of assent (affirmation) and ascent (it has an upwards movement and uplifts the soul, as the sound of the divine eagle or falcon.