Dodge bonus (not to be confused with Unarmored bonus) is a bonus to Armor Class, and sometimes Reflex saves, resulting from physical skill at avoiding blows and other ill effects.
Any situation or effect (except wearing armor) that negates a character's Dexterity bonus also negates any dodge bonuses the character may have (for instance, you lose any dodge bonuses to AC when you're flat-footed).
Dodge bonuses stack with all other bonuses to AC, even other dodge bonuses.
Dodge bonuses apply against touch attacks.