from http://en.wikipedia.org/wiki/Socionics

Nature of Functions
  • Function 1 - leading, program, primary, base, or dominant function. This is the strongest conscious function, and the most utilized function of the psyche. A person's outlook and role in life is largely determined by the nature of this function. One is generally very confident in the use of this function, and may defend it when challenged.
  • Function 2 - creative or secondary function, is second in influence only to the dominant function. It assists the dominant function in achieving its essence. One is generally less confident with the use of this function than with his dominant function. As a result, the creative function is sometimes less instrumental when a person is challenged or threatened, or when dealing with new and complex tasks and data.
  • Function 3 - role function, is a weak but conscious function. One generally tries to be at least adequate in areas where use of the role function is necessary. However, generally one has very little control or confidence over the role function, and criticism is painfully acknowledged with respect to it. Tactful assistance is required from one's dual-seeking function to overcome the problems associated with the role function.
  • Function 4 - place of least resistance or the painful function, is a weak and conscious function, in addition to being the weakest function of the psyche. One painfully perceives his complete inability to use this function, and reacts negatively to its imposition upon him. Tactful assistance is required from one's hidden agenda to overcome the problems associated with this function.
  • Function 5 - suggestive, or inspired function, is a weak and unconscious function which is largely lacked. One requires assistance from somebody confident in this function in order to overcome the difficulties it presents. When left to ones own devices, the suggestive function goes unnoticed.
  • Function 6 - actualization, the hidden agenda or estimative function. This is a weak and unconscious function which one often understands poorly. Nonetheless, this function has a strong influence over one's actions. Individuals requires assistance from someone who uses it confidently in order to understand it. Often an individuals is only aware that they are totally unaware of how to use this function.
  • Function 7 - observant or the ignoring function, the function of personal knowledge. This is a strong but unconscious function. One generally has a good grasp of this function, but attempts to limit its use considerably. Individuals will disregard this function when an argument calls for restraint or when it will be difficult to indulge in its essence.
  • Function 8 - demonstrative function. This is the strongest of the unconscious functions. As a result, it is so deeply rooted into the psyche that one is usually not consciously aware of its existence or utilization. Individuals will often identify their demonstrative function mistakenly when discussing 'who they are.'