Om or Aum Is the most important symbol in Hinduism it is considered the sound heard at the creation of the universe.
Divided into 2 categories Sruti and smriti
Sruti literally means "that what is revealed"
Smriti means "that what is remembered"
If a mortal dies where their soul goes depends on his previous action, thoughts, and time of their death. For example if a man is thinking about his family he will go to the heaven of ancestors.