In his Memorabilia Xenophon examines the charges against Socrates:
"Socrates is guilty of crime in refusing to recognise the gods acknowledged by the state, and importing strange divinities of his own; he is further guilty of corrupting the young."
Xenophon elaborates further on the trouble in which Socrates was embroiled because he followed principles instead of the will of the people. The boule was the council whose job entailed providing an agenda for the ekklesia, the citizen assembly. If the boule didn't provide it, the ekklesia couldn't act on it.
"At one time Socrates was a member of the Council [boule], he had taken the senatorial oath, and sworn 'as a member of that house to act in conformity with the laws.' It was thus he chanced to be President of the Popular Assembly [ekklesia], when that body was seized with a desire to put the nine generals, Thrasyllus, Erasinides, and the rest, to death by a single inclusive vote. Whereupon, in spite of the bitter resentment of the people, and the menaces of several influential citizens, he refused to put the question, esteeming it of greater importance faithfully to abide by the oath which he had taken, than to gratify the people wrongfully, or to screen himself from the menaces of the mighty. The fact being, that with regard to the care bestowed by the gods upon men, his belief differed widely from that of the multitude. Whereas most people seem to imagine that the gods know in part, and are ignorant in part, Socrates believed firmly that the gods know all things -- both the things that are said and the things that are done, and the things that are counselled in the silent chambers of the heart. Moreover, they are present everywhere, and bestow signs upon man concerning all the things of man."
By corrupting the young is meant he encouraged his students down the path he had chosen -- the one that led him into trouble with the radical democracy of the time. Xenophon explains:
"Socrates cause[d] his associates to despise the established laws when he dwelt on the folly of appointing state officers by ballot? a principle which, he said, no one would care to apply in selecting a pilot or a flute- player or in any similar case, where a mistake would be far less disastrous than in matters political. Words like these, according to the accuser, tended to incite the young to contemn the established constitution, rendering them violent and headstrong. "
Xenophon Translations by Henry Graham Dakyns (1838-1911) in the public domain.