Gandhi was often jailed for sedition. What was this crime?
Sedition is a term of law to refer to covert conduct such as speech and organization that is deemed by the legal authority as tending toward insurrection against the established order. Sedition often included subversion of a constitution and incitement of discontent (or resistance) to lawful authority. Sedition may include any commotion, though not aimed at direct and open violence against the laws, says Wikipedia.
The difference between sedition and treason consists primarily in the subjective ultimate object of the violation to the public peace. Sedition does not consist of levying war against a government nor of adhering to its enemies, giving enemies aid, and giving enemies comfort. Nor does it consist, in most representative democracies, of peaceful protest against a government, nor of attempting to change the government by democratic means (such as direct democracy or constitutional convention).