Once back in India, Gandhi led the fight for Indian independence from the British Empire. He organized non-violent civil disobedience campaigns. This was where large groups of the Indian population would do things like refusing to work, sitting in the streets, boycotting the courts, and more. Each of these protests are small by themselves, but when most of the population does them at once, it can shut down the country.
Gandhi was put in prison several times for organizing these protests. He would often fast (not eat) while he was in prison. The British government would eventually have to release him because the Indian people had grown to love Gandhi. The British were scared what would happen if they let him die.
One of Gandhi's most successful protests was called the Salt March. When Britain put a tax on salt, Gandhi decided to walk 241 miles to the sea in Dandi to make his own salt. Thousands of Indians joined him in his march.
Gandhi also fought for civil rights and liberties among Indian people.