When you create an new character in Arcanum, the option is there for you to choose a background for them. An interesting background will give your character bonuses to their skills and stats, but always at a cost (for example, the Bully background will grant you a +1 to Strength but incur a -1 to Intelligence). What backgrounds are available to your character is determined by your race and gender. The default background for all characters is "No special background", granting neither pros nor cons.
These are the backgrounds available: