Typically used with: Agility.
In short: get out of the way. Those who excel at Dodging are rather difficult to hit. Every attack of which a character is aware can be thwarted with a successful Dodge check. Less agile combatants may actually elect to evade attacks through parrying, but not all dangers can be smacked away with a weapon!
Characters who fail to remove themselves from harm's way often need a Guard check to see exactly how much hurt gets laid out.
Typically, a Dodge roll is used against an incoming attack by an opponent. The GM can institute a DL for a danger that has no opposed roll, for instance, a collapsing ceiling beam, or arrows from that devious trap you just triggered.
Dodge rolls are most often in direct opposition to Attack Rolls.