Stupid question, but what exactly are class skills in the Pathfinder RPG? I believe it means I get one "free" skill rank in that class, am I right in this assumption?
You get a +3 bonus if you have put ranks a Class Skill:
In addition, each class has a number of favored skills, called class skills. It is easier for your character to become more proficient in these skills, as they represent part of his professional training and constant practice. You gain a +3 bonus on all class skills that you put ranks into. If you have more than one class and both grant you a class skill bonus, these bonuses do not stack.