Makar means Crocodile(represents the materialistic world) & sankranti means to cross over or to change. So, Makar Sankranti is considered as an opportunity to get away from the clutches of this materialistic world. Makar Sankranti,also known as Uttarayan marks the transition of the Sun from Sagittarius(dhanu) into the zodiac sign of Makar(Capricorn) from the tropic of cancer on its celestial path or towards northern hemisphere. Sun, the universal source of energy , also the eye of the universe, makes us see the beauty of the nature. So, basically a thanks giving to God SUN is performed by some rituals like holy dip especially in river Ganges nd offering prayers to SUN god.
This also signifies the end of winters nd onset of spring.The nature begins to smile nd grow showing its happiness with new harvest nd joy.Colourful migratory birds start preparing for their return journey back home. The days r longer nd warmer meaning Sun slowly removes the darkness & ushers in the light of knowledge.14th jan also marks the equal hours of day & night...
Uttarayan is a six month long period & is considered as the day time of 'Dewtas' so is considered auspicious.
Flying Kites is the most colourful celebration mostly popular in Gujrat, Maharashtra & Rajasthan.The sky is full of colourful kites nd as the Sun sets floating oil lanterns r added to the kite's tail meaning removing darkness nd return to light, to warmth nd to life giving sun.
There r many mythologicaly imp. stories associated.... like 1.Bhishma pitamah despite being in pain, waited for Uttarayan for the final destination. 2.Lord Vishnu killed Madhu asura nd got to know as Madhusudan, 3.Bhagirath brought down Ganges...... etc but the main is... 4.Sun visits his son Shani ( the swami of makar rashi), who otherwise r not at gud terms nd fills his house with all prosperity.
So, it's a festival of reunion, of happiness, of colours,of harvest, of prosperity and of growth. It signifies a move from evil to gud, from darkness to enlightenment, from death to immortality!!