Attacks in close combat work like shots in shooting – each attack that hits has a chance to wound, the wounded model gets a chance to save, and if it fails is (generally) removed as a casualty. Each model base-to-base with an enemy model strikes with the number of Attacks (A) on his characteristics profile. In addition the following bonus attacks apply.
+1 Two Weapons. Models in base-to-base contact with a pistol/close combat weapon in each hand have an extra +1 Attack. Models with more than two weapons gain no additional benefit – you only get one extra Attack regardless of whether you have two or more close combat weapons.
+1 Charged. Models in base-to-base contact who launched the close assault that turn (ie charged) get +1 Attack on their normal profile for that turn only.
Models not touching an enemy, but within 2" of one, may make one Attack regardless of their profile, armament or whether they charged.
Diagram: Attacks. A model within 2" of an enemy but not touching gets One Attack. A model in base contact gets Two Attacks (1+1 for charging). A Space Marine Veteran Sergeant in base contact gets Four Attacks (2+1 for charging and +1 for being armed with two close combat weapons).