Durga is the Hindu goddess of motherhood as well as victory of good over evil. She is believed to be the power behind the work of creation, preservation, and destruction of the world. Since time immemorial she has been worshiped as one of the supreme powers of the Supreme Being.
Durga is depicted as having eight or ten hands. These represent eight quadrants or ten directions in Hinduism. This suggests that she protects the devotees from all directions. Like Shiva, Durga is also referred to as "Triyambake" meaning the three eyed Goddess. The left eye represents desire (the moon), the right eye represents action (the sun), and the central eye knowledge (fire).
There are many incarnations of Durga: Kali, Bhagvati, Bhavani, Ambika, Lalita, Gauri, Kandalini, Java, Rajeswari, et al. Durga incarnated as the united power of all divine beings, who offered her the required physical attributes and weapons to kill the demon "Mahishasur". Her nine appellations are Skondamata, Kusumanda, Shailaputri, Kaalratri, Brahmacharini, Maha Gauri, Katyayani, Chandraghanta and Siddhidatri.
Durga's form of transport is an enormous lion. The lion represents power, will and determination. Durga riding the lion symbolizes her mastery over all these qualities. This suggests to the devotee that one has to possess all these qualities to get over the demon of ego due to her mastery over all these qualities. This suggests to the devotee that one has to possess all these qualities to get over the demon of ego.
Durga possesses many weapons at her disposal. The conch shell in Durga's hand symbolizes the 'Pranava' or the mystic word 'Om', which indicates her holding on to God in the form of sound. The bow and arrows represent energy. By holding both the bow and arrows in one hand "Mother Durga" is indicating her control over both aspects of energy; potential and kinetic. The thunderbolt signifies firmness. The devotee of Durga must be firm like a thunderbolt in one's convictions. Like the thunderbolt that can break anything against which it strikes, without being affected itself, the devotee needs to attack a challenge without losing his confidence.