The snake around Shiva's neck reinforces a sense of stillness

The mountains, snow and the snake around Lord Shiva's neck is a symbol representing his sense of calmness. Self-contained and content, Shiva is a symbol of calm and peace. 

Story of Lord Shiva - Shiva Lingam

Lord Shiva is so often represented as a "lingam". Linga basically means a sign or symbol. So the lingam is essentially a symbol of the shapeless universal consciousness of Lord Shiva. 

The story of Shiva Lingam:
There are a few versions according to the Puranas of why Shiva is worshiped as a lingam and how this happened, of which I will relate one. There was a great sacrificial ceremony that was going to take place many hundreds of years ago. The great sage Narada Muni was invited to it and asked who would receive the effects of the sacrifice. No one could answer, so the sages who were present asked him who should receive it. Narada said that Sri Vishnu, Brahma, and Shiva were all eligible, but they would have to find out which one had the most patience and purity to be the receiver of the sacrifice. So he chose the great sage Brighu to learn the answer.

Brighu had many mystic powers and was able to travel to the domain of the demigods. So first he went to see Lord Brahma, but Brahma was preoccupied and did not notice Brighu’s presence. Feeling insulted, Brighu cursed Brahma, “You are so proud of your power of creation, you did not notice my arrival. For this you shall have no temples on earth.” Thus, there are very few temples of Brahma on earth. Next, Brighu went to see Shiva in Kailash, but Shiva also did not notice Brighu’s arrival. Brighu, again feeling offended, cursed Shiva to be worshiped only as a lingam on earth. This is the reason why Lord Shiva is primarily represented and worshiped as a lingam on this planet.  

 The Shiva-Lingam is a symbol of the Hindu deity Shiva as generative force of the universe. 

• “Shiva” also means that in which the creation lies dormant after the annihilation. So, one explanation is that the lingam is a representative of the dormant universal consciousness in which all created things rest after the cosmic annihilation.
• It also represents the pradhana, the potential but unmanifested ingredients of the material world.
• Another explanation is that Shiva means auspicious. So the linga is the shapeless symbol for the great god of auspiciousness. It is intended to bring the shapeless unknown into our attention.
• The yoni upon which the lingam often sits represents the manifest universal energy. From the unmanifest comes the manifest energy, through which all other things are created.
• The yoni, which is a symbol of Shakti, combined with the lingam, is a symbol of the eternal union of the paternal and maternal principles, or the positive and negative, or the static and dynamic energies of the Absolute Reality. It is the communion of the eternal consciousness and dynamic power of the Shakti, the source of all actions and changes.
• It is also the symbol for the creation of the universe through the combination of the active energy of Lord Shiva and his wife Shakti. This is how Lord Shiva and Durga are considered the parents of the universe.
• The symbolism of the lingam and yoni also represents the base of the spine, meaning the Muladhara chakra, upon which the kundalini (Kundalini) is resting, waiting for awakening.

Parts of a Linga:
The lingas in the temples are often formed in three parts.

1. The lowest part is the base square called the Brahmabhaga or Brahma-pitha, which represents the creator Brahma.
2. The next part in the middle is the octagonal Vishnubhaga or Vishnu-pitha, which signifies Lord Vishnu the sustainer. Both of these parts form the pedestal.
3. The top cylindrical portion is the Rudrabhaga or Shiva-pitha, which is also called the Pujabhaga since this is the worship-able part. The top portion is also meant to symbolize the projecting flame of fire. This flame also represents the destructive aspects as well as the preserving power of God.

There are twelve important shiva linga  temples scattered across India. They are found in Kedarnatha, Kashi Visvanatha, Somnatha, Baijnath, Ramesvare, Ghrisnesvar, Bhimasankar, Mahakala, Mallikarjuna, Amalesvar, Nagesvar, and Tryambakesvar. The five Pancha Bhuta Lingas in India are located at Kalahastisvar, Jambukesvar, Arunachalesvar, Ekambesvara at Kanchipuram, and Nataraja at Chidambaram. The temple of Lord Mahalinga at Tiruvidaimarudur (Madhyarjuna) is also a great temple in South India.

Composed by : Sakthi Sakthithasan

(Thank you - Quora for the content )