Socrates was an Athenian philosopher. He was born 470 BCE and died 399 BCE. There are only three contemporaries of his whose works about him still survive to this day, their being Plato, Xenophon (an Athenian general), and Aristophanes (in his play "The Clouds", who probably just used to Socrates to represent philosophers in general). Socrates was supposedly the first philosopher to put the main focus on how one should live their life, stressing ethics and morality. He was a short, pudgy man with a snubbed-nose and usually walked around barefoot. He was a soldier for Athens in the Peloponnesian War and was supposedly an astonishingly disciplined, austere soldier of great bravery. He had a wife, Xanthippe, and three sons, and worked with stone. He spent much of his time in the Agora (Greek market place) seeking wisdom that others might have, or picking verbal arguments, however you want to look at it. When Socrates would find people that believed themself to be wise and very knowledgeable about things he would ask them a series of questions which the pretender to knowledge would answer and Socrates would lead them into a trap to force them to contradict something they had said before, thus demonstrating for them that they actually did not have the knowledge they pretended to have. This attracted a large crowd of younger boys who enjoyed watching Socrates make fools out of respected men.
In 399 BCE Socrates was put to death by the city-state of Athens. His trial is described many years after the fact in Plato's and Xenophon's apologies (Xenophon wasn't there and learned of what happened in the trial from someone else). It is unsure exactly why Socrates was found guilty. The formal charges against him were introducing new gods to the pantheon and corrupting the youth of Athens, but the reason why he was found guilty is probably due to some other reason. One reason may have to do with a particular battle from the Peloponnesian war. There was a naval battle in which Athens won and left the scene of the battle in a hurry (Battle of Arginusae in 406 BCE), leaving many Athenian sailors in the water. Athens had one trial for the group of generals from the battle. Socrates angered people when he argued that each general should have his own trial to account for what he did after the battle. Another reason might be that the recently reinstated democracy in Athens found Socrates guilty simply because of his ties to Critias, one of the 30 tyrants who were put in place to govern Athens by Sparta after the war. Or perhaps it was an unconscious reason, like Athens was in a state of confusion and humiliation following their loss in the Peloponnesian war, and they reacted harshly concerning Socrates, who had associations with the war (a Greek history professor of mine, speculated this reason to me). Or it could simply be that Socrates had annoyed too many people by making them look like fools in front of others. Anyway, the trial had two parts. The first part was made up of an argument on both sides about why the accused is either guilty or is innocent of the charges made against him. If the accused is found guilty then the second part of the trial is for the defendant to argue for a different punishment than what the prosecution had asked for. His accusers wanted his death. Socrates was found guilty of the crime by 281 to 275. But after Socrates made his argument for the alternate punishment of death being a small fine that his friends would pay, and then mentioned that Athens should actually pay him for being an asset to Athens and showing people when they did not have true knowledge, the punishment of death was agreed upon by 361 out of the 551.
It is difficult to be certain of Socrates's philosophy. One must try and extract it from Plato's and Xenophon's writings. A well known quote of Socrates's is "the unexamined life is not worth living". As was mentioned above, Socrates stressed being a virtuous person. He believed that people perform evil actions only out of ignorance of the truth because everyone really seeks the Good (which refers to what is good for oneself). So one must know oneself in order to know what choices they should make in life, and be self-disciplined (this included not letting oneself be controlled by money, lust, or power) in order to make those choices. This is one of the reasons why Socrates wished to show others of their ignorance, so they wouldn't be misled by false knowledge and can know the Good. Also Socrates believed that doing harm to others actually does more harm to oneself, and he espoused the belief of turning the other cheek. A second reason why Socrates wished to show others their ignorance was because Socrates believed that the wise man knows he knows nothing. Socrates believed that the knowledge of mankind is petty and flawed compared with the knowledge that the gods have. Socrates didn't believe that the gods were as they are described in Homer and Hesiod, but instead the gods were good, moral, just beings. In Plato's Phaedo, Socrates appears fairly sure that there is an afterlife, and that life existed for each of us before we were born. That the act of obtaining knowledge in this life is actually a process of trying to remember knowledge that one had in the life before. That is one of the reasons why the Socratic method (illiciting answers from someone by asking them questions, and their answers would lead them to a conclusion) was believed to be useful.