On this point of sail (also called running before the wind), the wind is coming from directly behind the boat. Running can be dangerous to those on board in the event of an accidental jibe.
When running, the mainsail is eased out as far as it will go. The jib will collapse because the mainsail blocks its wind, and must either be lowered and replaced by a spinnaker, or set instead on the windward side of the boat. Running with the jib to windward is known as 'gull wing', 'goose wing', 'butterflying' or 'wing and wing'. A genoa gull-wings well, especially if stabilized by a whisker pole, which is similar to but lighter than a spinnaker pole.