Gandhi is unequivocally the most important person in India's history. He started his career as a lawyer in South Africa and was very intelligent and pragmatic. He was the man solely responsible for the freedom of India from the British Empire.
The English had great influence in India since the 1600's and colonized it in the 1700's. While India benefited from this relationship is some tangible ways, they were ultimately second class citizens in their own country. The English, on the other hand, were able to utilize the resources for profit and recruit Indian soldiers for their military use. The English had no interest in losing the colony.
Gandhi, as a devout Hindu, did not believe in violence. He utilized the method of civil disobedience to achieve his political goals for India. Marches, boycotts, and skillful use of the international press were all strategies that he used to embarrass the British. He was successful despite many challenges within the Indian religious, economic, and political environment.
India, as a population, was not unified with factions of Hindus and Muslims that did not really like each other. There was also a segment of the population that benefited from British colonial rule. Additionally, a natural disharmony among the different castes in India existed. Gandhi was able to unify these different factions to the common goal of independence.
In August of 1947, the British, faced with post-war economic and military challenges finally relented and granted India its independence. Gandhi is widely admired by Indians as the "father of India" for his efforts in making this independence a reality.