Murtis are Yogic Statues
When the Yogic statues are energized, they are often termed as Murtis. A murti can be made of metal (brass or bronze), stone or marble and is usually on the main altars (sanctum sanctorum) in temples.

You can energize these Murtis in a couple of ways:
One technique is called Prana Pratishta where usually the priest invokes Vedic mantras to imbibe Prana into the murti. This is usually done in temples. I don’t recommend this method for most householders because you then have to do Puja everyday to the murti and dress and feed the murti. We live busy lives and it’s difficult to meet this commitment.
What I recommend is Mantra Pratishta where the Murtis are energized by mantras. That’s what we do in our temple. You can actually measure the energy in these Murtis by a technique called GDV (Gas Discharge Visualization) which is an enhancement of the aura photography technique (Kirlian effect). Several companies had made these measurements on Murtis and have shown they hold energy and that’s why the Murtis need to be metal, stone or marble.

At first sight, these deities may appear as polytheistic. When you go deeper, you realize that they are different facets of the One. For instance, such Lakshmi is for abundance, Saraswati for knowledge, Shiva for transformation, etc. – so it can be termed Monism. When you go deeper into the teachings of the Upanishads (Advaita Vedanta), you realize that it’s actually non dualism. You cannot objectify the Self, it is the eternal I Am. If you talk or even think about it, it’s not that. That’s why it’s termed non dualism or Advaita (Not Two).

The origin of these deities comes from the Puranic scriptures which is often called the fifth Veda. Often the Vedic philosophy of the Upanishads is extremely rigorous, complex and need years of study under a Guru who is a Shrotriya Brahmanishta (one who is enlightened and can teach you the method in the Upanishads). Most people in ancient India (not unlike today) had regular jobs and businesses and didn’t have the time to commit to such a study. That’s why these deities with their myths and symbols came about to explain the same philosophies in very vivid and colorful detail. Most children in India grow up with these myths. Story telling is an important art in this tradition.