The last letter of your type “points to” the function you use with the outside world—either your perception function (S or N) or your judgment function (T or F).

• If you are an ENTJ, for example, your type ends in J, so you use your judgment function, which is Thinking, in the outside world.
• If you are an ISFP, then you use your perception function which is Sensing, in the outside world.

For those who prefer Extraversion, the dominant function is extraverted because Extraverts use their favorite function (dominant) in their favorite world (the outer world.)

For those with a preference for Introversion, the dominant function is introverted, used in their inner world, and what they show to the outside is their auxiliary or second favorite function.