According to legend, Goddess Parvati gave the Vel, or lance, to Lord Muruga on the Thaipusam day to vanquish the Asura army. Thaipusam is observed on the Pusam star in the Tamil month of Thai , which falls in January - February.
Lord Muruga defeated Tarakasuran and other demons using the vel. This is why most images of Lord Muruga have him carrying the powerful vel.
Thaipusam is mainly celebrated in the Tamil speaking world. In India, it is celebrated in the Southern State of Tamil Nadu and in parts of Kerala, Andhra Pradesh and Karnataka. Thaipusam celebration at the Batu Caves in Malaysia has become world famous. It is also celebrated with much fervor in Singapore. Devotees carry Kavadi to Murugan temples on this day. Nowadays, Thaipusam celebrations garner international attraction for the body piercing with vel by devotees.