Explained: Wildfires burn across western US and Canada as residents are evacuated

Wildfires are burning across the western U.S. and Canada, forcing evacuations

Mop-up operations

Firefighting work done near containment lines after a fire has stopped growing, to extinguish remaining hot spots

Containment lines

Boundaries firefighters establish to stop a wildfire from spreading further

State of emergency

An official declaration by a government allowing it to mobilize additional resources and assistance during a crisis