Editing Ogre:CharacterCodex:Introduction (section)

====Favorable and Unfavorable Conditions====
Some situations may make a skill easier or harder to use, resulting in a bonus or penalty to the skill. A modifier can affect your skill roll or the DC of the task to be done. Modifiers are always describe in four parts, for example, a +2 insight bonus to Spot check. 

* The first part (+2) is the value you add or subtract from a skill check or a DC.
* The second part (insight) is the type of modifier that you receive. As a general rules, modifier of the same type do not stack, you take only the best bonus or the worse penalty.
* The third part (bonus) explains if the modifier is advantageous for the player or not. A bonus is always advantageous for a character while a penalty always hinders the character. 
:''For example a +2 circumstance penalty to Climb DC makes the DC of a check higher and more difficult to do.''
* The last part (Spot check) gives the skill that the modifier affect and if it is applied to the skill check or to the skill DC.