Dashera (दशहरा – Dashara)

Dashera (दशहरा – Dashara) comes from Sanskrit words Dasha-Hara which means the defeat of ten headed demon (Ravan) of Hindu methology. It is celebrated on the tenth day of the Hindu lunar month of Ashvin (अश्विन) which usually falls in October as per Gregorian calendar. In spiritual sense, this signifies the victory of good over evil. In many part of the country, this festival is also known as Vijayadashami (विजया दशमी). The word, Vijaydashami, is derived from Sanskrit words, Vijay (Victory) and Dashami (Tenth Day) and combined they signify the tenth day of  the month of Ashvin on which Lord Ram, the seventh avatar of Vishnu, has defeated Ravan (रावण), a demon king from Hindu mythology. The entire narrative of events is recorded in the epic Ramayana (रामायण), a Hindu scripture. This festival also
marks the festival of Diwali which falls after 19-20 days after it which signify the return of home of Lord Ram to Ayodha, an ancient city in North India, after defeating Ravan and a long exile of 14 years.  Diwali is the biggest festival of India which mark the return of Lord Ram in the evening and his welcome by the residents of Ayodhya who lit their city with lamps (called Deepak or Diya ). Since then, this day is celebrated as Deepawali (दीपावली) or Diwali (दीवाली).

This festival also marks the end of Ram Lila (राम लीला), the dramatic re-enactment of the life of Lord Ram which also describe ten day battle between Lord Ram and Ravan, as described in the Hindu religious epic, the Ramayana.

On this festival, people goes to temples and many performs Havan (rituals) to get rid of 10 bad qualities or negativity from the household just like getting ride of ten headed demon, Ravan. The ten heads of Ravan are represented by Kama Vasana (Lust), Krodha (Anger), Moha (Delusion), Lobha (Greed), Mada (Overpride), Matsara (Jealousy), Manas (Mind), Buddhi (Intellect), Chitta (Will), Ahankara (Ego). In the evening, the large effigy of Ravan is also burnt which is the part of the re-enactment of Ram Lila. 

Read more at :  

• Vijayadashami In wikipedia 

• The History & Origin of Durga Puja