In the M12 Rules System, characters have four Psychological Characteristics (Attributes) and four Physical Characteristics - the two groups each have Strength, Resistance, Manipulation, and Agility. Characteristics have a Dice Score of 2-6 (the rules support either pool purchase or randomization or array distribution). Characters have other traits defined such as State of Mind, Field of Expertise (very roughly analogous to a Class), and Skills. Skills have a Base Value which is a negative number that must be overcome before the character is considered "skilled". Skills are purchased from a large point pool resulting in highly skilled characters.
The M12 Rules System utilizes dice pools of D12 against a target number of successes. The dice pool size is determined by the relevant Characteristic's Dice Score. This is modified by the character's Skill rating (if appropriate) to find a resolution number which is compared against a Difficult Level.
The Truth Is Out There is a specific genre and setting for the M12 Rules System (apparently, the only one ever created). It adapts the X-Files television series to table-top role-playing. Characters are "Agents", investigating paranormal phenomena.