The misconception about Shiva Lingam

God is not an idea, it is a consciousness.

Linga represents the Lord of the Universe.

Shiva is represented by the Lingam or Mark, which is manifestly the Creative power of Divinity.
Shiva-lingam is a sign by which Shiva is symbolized. The word Linga means an emblem, symbol or a mark that points to an inference.
The Sanskrit-English Dictionary edited by P. K. Gode and C. G. Karve is widely regarded as an authoritative work and it gives a wide range of meanings for lingam:"The primary meaning given is: “A mark, sign, token, an emblem, a badge, symbol, distinguishing mark, characteristic.”
Linga Purana states, 'The foremost Linga which is devoid of smell, color, taste, hearing, touch, etc, is spoken of as prakriti (nature).
In the Upanishads , Linga is invariably used in the sense of a mark or a symbol.

Avyakteshu parah purusho vyapako Linga yeva cha

Na cheshita naiva cha tasya Lingam

Mahadadyam Vishesantam Lingam

Many a time the word Yoni is found in the Upanishads, but it is taken to mean not as a female genital organ but merely as the source or prima causa of the Universe.

The Linga is only the outward symbol of the formless being, Lord Siva — who is the indivisible, eternal, auspicious, ever-pure, immortal essence of this vast universe. He is an indweller, the undying soul seated in one's heart, innermost Self or Atman and who is identical with the Supreme Brahman.

It is an amorphous icon of Shiva represents the being which is beyond the 36 tattvas, where as an anthropomorphic Nataraja that represents creation, an icon representing Siva within all 36 tattvas.

Why to misunderstand the Lingam ?

To some people it is difficult to grasp the meaning of a Shiva Linga.The worship of this shaft horrified many early Western visitors to India and still misunderstood by others.

The Linga is certainly a bisexual symbol but not a phallic symbol alone. The shaft of the Linga of Shiva is set in a circular base, called a "seat" - Aaavudai in Tamil . It represents the female divine energy – Shakti, personified as Shiva's female half . The eternal union of Shiva and Shakti gives birth to the whole Macrocosm, represents the human being and the universe with its physical and also invisible aspects

In classical Hinduism, the lingam of Shiva is the center of worship, the male aspect represents pure consciousness, which is inactive; the female aspect symbolizes the primal force, which is active. Shiva is the masculine energy, the supreme lord, the great ascetic and meditator. The Shiva Lingam , stands for an eternal column of light, the purest form of Shiva.

In Tantric Hinduism, the yoni of Shakti is added to the Lingam of Shiva to form a symbol incorporating the genitals of both sexes, thereby symbolizing the creation of the universe.

Many ancient civilizations recognized the wonder of this concept. In the oriental philosophy /in the Eastern thought, the solar, positive male aspect is called Yang, and the lunar, negative female aspect is called Yin. Yin and Yang are inseparable and makes up the very life of the Universe.