A lingam (“sign, symbol or mark”) is an abstract representation of the Hindu deity Shiva, used for worship in temples, smaller shrines, or as self-manifested natural objects.The lingam is often represented as resting on disc shaped platform called a yoni or pitha.
Literal meaning of Lingam in ancient hindu language Sanskrit is Symbol. Word lingam is also used in conjunction with other words like purling(Male), Striling(Female) etc. Linga word is also used for male body part, due to that there is confusion or misinterpretation of Shiv lingam to the same. But actually lingam is word for the symbol in Sanskrit. Word used for male body part in Sanskrit is “Shishna”. As Sanskrit is ancient langague of hinduism so it is clear that shiv lingam represent symbol of lord Shiva. There is anoter myth that yoni is female body part actually Yoni means spicies or nature in Sanskrit. There are different types of yonis(species) considered in hinduism for example Pashu yoni ( Animal species), Manushya yoni( Human species). Just to cross check validate the usage of this words. If lingam is Penis then why it is being used in word Striling(Females). There is no penis as such in Stris(Females). So it proves that Lingam is basically means Symbol. Same reasoning can be put across for yonis.
The Hindu scripture Shiva Purana describes the origin of the lingam, known as Shiva-linga, as the beginning-less and endless cosmic pillar (Stambha) of fire, the cause of all causes. Lord Shiva is pictured as emerging from the cosmic pillar of fire – proving his superiority over the gods Brahma and Vishnu. This is known as Lingodbhava. The Linga Purana also supports this interpretation of lingam as a cosmic pillar, symbolizing the infinite nature of Shiva. According to the Linga Purana, the lingam is a complete symbolic representation of the formless Universe Bearer – the oval-shaped stone is the symbol of the Universe, and the bottom base represents the Supreme Power that holds the entire Universe in it. A similar interpretation is also found in the Skanda Purana: “The endless sky (that great void which contains the entire universe) is the Linga, the Earth is its base. At the end of time the entire universe and all the Gods finally merge in the Linga itself.” According to Jaggi Vasudev the lingam is considered the first form to arise when creation occurs, and also the last form before the dissolution of creation. In the Mahabharata, at the end of Dwaraka Yuga, Lord Shiva says to his disciples that in the coming Kali Yuga, He would not appear in any particular form, but instead as the formless and omnipresent.