The concept of God as Supreme and the idea of seeing God in everything in the world is very popular.
The Taitreeya Upanishad says –
Maatru Devo Bhava - May the mother be treated as God.
Pitru Devo Bhava - May the father be treated as God.
Aachaarya Devo Bhava - May the teacher be treated as God.
Athithi Devo Bhava - May the guests be treated as God.
(i.e.) the idea of worship of God as Supreme, but at the same time honoring the manifestation of God in people around us is a unique concept found only in Hinduism.
Every form of the Lord has a subtle metaphysical and spiritual aspect to it. Lord Shiva for instance is described as having five faces, ten hands, fair in complexion, smeared with ashes from the burial ground, wearing skull garlands and snakes all over his body, and seated in a meditative trance. The picture would make us shudder and wonder, why at all should Lord be so ‘disgusting’. Insight is needed to understand the ‘Tattva’ i.e. the truth behind the appearance. The five heads refer to the five-fold actions of creation (Srishti), sustenance (Sthiti), destruction (Samhaara), dissolution to subtle elements (tirodhana), and benevolence (anugraha). These are the functions of the Lord for the welfare of the individual soul.
The ten hands refer to the 10 organs of action and knowledge, which should be fully under the control of the mind. The skull garlands etc., represents the acceptance of all things likable and deplorable with the equanimous state of mind, on the part of the devotee, to attain salvation. The ashes on the body are a pointer to the fact that the body or for that matter anything in the world is momentary and is destructible, thus to cling on to worldly affairs is detrimental for spiritual progress. Every true seeker would discover many such inner-meanings when he searches for God with utmost sincerity. Hinduism is not pantheistic (belief in many Gods) as misunderstood, but panentheistic (seeing the same Lord in many).
Worship
The worship of the Lord on the part of the devotee is to be motivated by nothing else other than pure devotion. That the Lord bestows, what is best for the devotee, without being asked for, is the unshakable faith. Motivated by pure love, the devotee can indulge in either external worship (Bahir pooja) or internal worship (Antar pooja).
Antar Pooja or internal worship is to contemplate and offer all the honors to the Deity by mentally conceiving them. But to practice this, the devotee should belong to a higher order of Bhakti. To mentally visualize and worship uninterruptedly is a great task by itself, which is fit to be undertaken by people with a higher order of concentration and practice of withdrawal of senses from the external world.
Bahir – Pooja :
For the devotees who are yet to attain great spiritual heights, the scriptures (shastras) prescribe an external mode of worship. A devotee would invoke the Supreme Self with appropriate procedures in external tangible objects such as idols, pictures, diagrams (yantras), pebbles or metallic forms, etc. In doing so, the devotee has a firm belief that the Lord is present in all His glory, in the object wherein He is invoked.