The night of the union of Shiva and Parvati is known as Maha Shivratri. Although Shivratri is celebrated on the Chaturdashi Tithi of Krishna Paksha of every month, Shivratri, which is celebrated on the Chaturdashi of Falgun month, has special significance.
Shivaratri is great festival of convergence of Shiva and Shakti. Each month, Chaturdashi Tithi during Krishna Paksha is known as Masik Shivaratri.
According to Indian Mythology, in the midnight of Maha Shivaratri, Lord Shiva was appeared in form of Linga. Shiva Linga was first worshipped by Lord Vishnu and Lord Brahma. Hence Maha Shivaratri is known as birthday of Lord Shiva and devotees worship Shiva Linga during Shivaratri.
It is believed that the fasting of Maha Shivratri starts from triyodashi itself and from this day people start taking sattvic food. Some people start fasting from triyodashi. On the chaturdashi, after taking the bath people take sankalp of fast the whole day. On this day devotees offer Bhang, Dhatura, sugarcane, plum and sandalwood to their deity Lord Shiva. On the other hand married women offer bangles, bindi and vermilion, symbolising suhaag to Mother Parvati. On this day only fruits are consumed by devotees and consumption of salt is prohibited, if they ant they can consumed rock salt only.