There are three kinds of skill checks that can be made: active, opposed, and passive. An active check is one in which you roll a die, add your bonus, and compare it to a fixed DC. If you meet or beat the DC, you are successful. A passive check is one in which someone or something else rolls a die and adds their bonus, and your skill determines the DC ƒ in this case, the DC is almost always equal to 4 + your skill modifier. Passive skill checks occur generally when your character is not directly acting, or does not necessarily have knowledge about what is happening. An opposed skill check is when two characters make active skill checks, and the one with the higher result wins. In the event of a tie, unless otherwise specified, both characters reroll.