Close combat is a swirling melee of fighters leaping forward, spinning, hacking and slashing at one another. As well as fighting hand-to-hand, warriors will be firing at point blank range at any target that presents itself.
Models in base-to-base contact with the enemy will fight with their full number of Attacks and count the benefits of any special close combat attack forms they have. All models that are within 2" of a friendly model which is engaged in combat will take part in the fighting as well, not just those in base contact. They only get a single Attack though, regardless of the number of Attacks on their profile, and get no benefit from any special close combat attack forms they have. Such models are referred to as supporting models.
Diagram 5: Models in base contact fight with their full number of Attacks. The model supporting in 2" makes a single Attack and may not use special close combat attacks.