The below mentioned article provides an essay on Saivism.
The other popular sect of Hinduism is Saivism. Like Vishnu, Siva is also worshipped by the majority of the Hindus. Of course, there had been rivalry between the two sects and each claimed superiority of their own god over the other but differences were mostly reconciled and now both of them are equally revered by the Hindus.
The origin of Siva can be traced to the concept of Rudra in the Rigveda. Probably, he found his place among Aryan gods because of the influence of the Dravidians who had a similar god among them called Pasupati. In the Yajurveda, he is referred to as Sambhu or Shankar. In the Atharvaveda, he is regarded as the Supreme God while in the Svetasvatara Upanishad, his spouse Uma or Parvati, is provided a similar position.
Thus Siva rose into prominence with the passage of time. By the time of Sutras, Saivism had acquired all its essential features. We find references of the worship of Siva in the form of Linga and descriptions of the wife and sons of Siva in Graha-Sutras. By that time, the wife of Siva too had acquired the status of an independent goddess. She was called by various names like Mahakali, Mahayogini, Durga, Sankh-dharini, etc.
In the Ramayana and the Mahabharata, Siva and his wife have been referred to at many places. In the Ramayana, Siva has been named as Maheswar, Mahadeva, Shankar, etc. while his wife has been called Uma or Parvati and has been described as the daughter of the Himalayas. In the Ramayana many episodes concerning Siva have been given like falling of the Ganges on earth, destruction of the Yajna of Daksya, birth of Skandha, son of Siva, etc.
In the Mahabharata, Siva has been referred to more than the Ramayana and emphasis has been laid on his worship and Bhakti. However, the rise of Saivism, with a philosophy and organization of its own, can not be traced back earlier than about the beginning of the Christian era. The sect, probably, was started by a person called Lakulin or Nakulin near about the beginning of the 2nd century and, by the beginning of the Chiristian era, Saivism became popular all over India and by the Gupta-age became as much popular among the Hindus as was Bhagvatism.
Afterwards, Saivism was divided into four important schools, viz., Pasupata, Saiva, Kapalika and Kalamukha. However, Siva is worshipped most in the form of the Linga (phallus) because of the influence of another sect of Saivism called Lingyat. Saivism is now a part of Hinduism and the worship of Siva is most popular among the Hindus.