The Game Classes Races Combat Area Descriptions Movies Screenshots Official FAQ Unofficial FAQ 3rd Ed. The combat sequence can be quite complex with speed and damage modifiers coming most commonly from physical attributes of the character and magic enchantments. Before combat can be explained you must understand what your AC is. This starts at 10 and continues up.
Higher numbers are always better.
His attack value after modifications for skill and other factors comes to 25. However, the orc's AC is only 20 so Garn hits the orc and causes damage. The damage done is determined by the type of weapon, in this case a long sword, and any modifiers such as from enchantments. An attack may also cause a critical hit which would inflict much greater damage. If he rolls a hit the second time, he's caused a critical hit.