Answer:
   
   This is a very broad question, hence, the answer is going to be
   painfully oversimplified. Jewish tradition teaches that G-d revealed a
   system of law to the Jewish people in the Sinai desert during their
   exodus from Egypt. This system includes 613 commandments, each is
   composed of numerous laws. No one could actually keep all 613; some
   are encumbant only on men, some only on women, some on the king, some
   on the preisthood, many require a standing Temple on Mt Moriah in
   Jerusalem, etc. And some, like the laws of divorce, you don't really
   want to be in a situation where there is a need to invoke them. That's
   for Jews, who have a covenant with G-d to be "a kingdom of preists and
   a holy nation".
   
   Non-Jews needn't do all that. They have all of 7 commandments, which
   divide into 66 chapters of laws, and myriads of details. These are
   part of G-d's covenant with Noah. These are called the "Noachide"
   laws, and are listed in the answer to [5]Question 12.19. The basic
   seven laws are: (1) Don't worship other gods, nor be an atheist; (2)
   Don't murder; (3) Don't commit certain sexual relations (including but
   not limited to incest); (4) Don't eat flesh from a living animall; (5)
   Don't blaspheme; (6) Don't steal; (7) Have a legal and penal system.
   
   Speaking philosophically, being good is usually defined in traditional
   Jewish sources in terms of three relationships: how one relates to
   G-d, to others, and to oneself. That last one needs some explanation.
   A person should develop their human nature, and rise above those
   traits we share with other mammals. Looking again at the first three
   of those Noachide commandments, idolatry is the ultimate violation of
   one's relationship with G-d; murder, of one's relationship with
   others; and sexual hedonism, of how one relates to oneself. One step
   down, we have blasphemy against G-d, stealing from others, and being
   cruel in one's pursuit for food. The last is society's responsibility
   to its members in pursuing the above.