Short answers, pulled from the story.
Socrates was charged with two offences at his trial in 399 BC: impiety against the pantheon of Athens by introducing new gods, and corruption of Athenian youth. His accusers were Anytus, Meletus, and Lycon.
The three accusers were Anytus, a wealthy Athenian who acted on behalf of craftsmen and politicians; Meletus, a younger man who acted on behalf of poets; and Lycon, who represented the interests of professional rhetoricians. Socrates identified Anytus as the true driving force behind the prosecution.
Socrates proposed free meals in perpetuity at the Prytaneum, the public dining hall of Athens, as his counter-penalty. He eventually settled on a fine of one hundred drachmae, though his supporters Plato, Crito, Critobulus, and Apollodorus offered to pay three thousand drachmae on his behalf.
The jury voted Socrates guilty by a relatively narrow margin. Socrates said he would have been acquitted if thirty more jurors had voted in his favour. Diogenes Laertius later recorded that 280 jurors voted for the death penalty and 220 voted for a monetary fine (2.42).
Socrates said he questioned them to resolve a paradox from the Oracle of Delphi. His friend Chaerephon had asked the prophetess Pythia whether any man was wiser than Socrates, and she answered there was none. Socrates, believing he possessed no wisdom, went looking for someone wiser to bring to the Oracle as a counter-example, and found that every apparently wise person lacked genuine self-knowledge.
The Apology is one of four Socratic dialogues Plato wrote covering the final days of Socrates, alongside Euthyphro, Crito, and Phaedo. The Apology depicts the trial itself; the Crito discusses the nature of justice; and the Phaedo covers the nature of the afterlife in Socrates's final conversation before his execution.