Lord Kartikeya is a Hindu god, the son of Shiva and Parvati, and is a much revered deity especially in South India. He is known by various names like 
Murugan, Shanmukha (Shanmuga), Subhramanian, Shadanana, Guha, Senthil, Saravana, Kumaraswamy and Skanda. Kartikeya is quintessentially brave, intelligent, and perfection personified because of which he is worshipped as the god of war and victory. He is also the brave leader of god's forces and was created to destroy demons, symbolising negative tendencies of human beings. In North of India Kartikeya, also called Kartik, is believed to be the elder son of Shiva and Parvati but his devotees in South believe him to be the younger son with Ganesha being the elder offspring of Shiva and Parvati.
Legend says that because Shiva and Parvati would shower Ganesha with more love, Kartikeya decided to leave Kailasa and move to the mountains in South and did not change his mind in spite of being urged by Shiva himself. And this is how he began to be worshipped in South India more than in North.
Origins of Kartikeya
According to the Skanda Purana, Shiva's first wife Sati angrily immolated herself after she felt insulted by her father Daksha when he didn't invite Lord Shiva for a Yagna Ceremony and further insulted Him. An irate Lord Shiva then destroyed the Yagna with the help of ganas. An ascetic Shiva was married with great difficulty the first time around and a second marriage was nearly impossible. Taking advantage of the fact the demons - Tarakasur and Surapadma thought the boon of being killed only by Lord Shiva's son would make him invincible.
Kama, the God of Love, awakens Lord Shiva from His penance to remarry Him to Goddess Parvati. Angered by the interruption in his meditation, Lord Shiva burns Kama to ashes with His third eye though He does fall in love with Goddess Parvati. Lord Shiva's hands His fiery seed fire to Agni who can handle it till the radiance becomes Shiva's offspring. Unable to bear the heat, Agni gives the radiance to Ganga who deposits it in a lake in a forest Sara Vana where Kartikeya is born (giving him the name Saravana) with six faces - eesanam, sathpurusham, vamadevam, agoram, sathyojatham and adhomugam, and hence the name Shanmuga or Shadanan. Kartikeya was cared for by six women symbolising Pleiades (Kritika in Sanskrit) and thus got the name Kartikeya.
Ideals that Kartikeya Represents
Kartikeya's weapon is Vel (spear) in one hand, which is also called as Shakti since his mother Parvati has given all the power to the spear, and he blesses his devotees with the other. The god of war mounts a peacock symbolising piety and subjugation of all sexual desires and destruction of bad habits and negative influences symbolised by the serpent that is clutched in the peacock's claws.
Karthikeya represents power and strength and worshipping him can get rid of woes and give the worshipper strength. Kartikeya destroyed the demon Tarakasur on the seventh day of his birth. He is known to be the most masculine and fierce among Hindu gods. Known for his valor and as the protector of dharma, Kartikeya has slained several demons like Krauncha, Banasura and Pralamba. He is also always youthful, which gives him the name Kumara (Sanskrit for youth). As Shadanan, Kartikeya has six heads, each standing for the five senses and the mind. The six heads also help him keep an eye in all directions so that he can combat problems coming from any direction. As war god with six faces, Kartikeya also teaches his devotees to battle through life fighting off bad people who could lead you to the wrong path of lobha(greed), kaama (sex), krodh (anger), moha (passion), mada (ego), and matsarya (jealousy).
Kartikeya as the Supremely Intelligent God
Kartikeya was supposed to have begun his education under none other than Lord Brahma Himself. But on the first day of his education Kartikeya asked Lord Brahma the meaning of Om. Lord Brahma described it on twelve thousand verses but Kartikeya was unsatisfied. When his father Lord Shiva explained the significance of Omkara in twelve lakh verses, he found that insufficient as well and said that Omkara can be explained in twelve crore verses, making Shiva proud of his son's intelligence and knowledge. Shiva then sent Kartikeya to live on earth for the welfare of mankind.
Wives of Kartikeya
In the North of India Kartikeya is believed to be a bachelor (Bramhachari) while in South He has two wives Devasena (Amruthavalli or Devayani) who is the daughter of Indra thus giving Kartikeya the name Devasenapati (also meaning the commander of the army of gods) and the daughter of a tribal hunter named Valli (Sundaravalli).