http://www.innerexplorations.com/catpsy/t1c1.htm
This is a pretty good description. They describe all of the functions pretty well too, pretty much like cliff notes on what Jung wrote about. This theory has a lot of explanatory power when it isn't completely misunderstood and abused.
I highlighted stuff cause I wanted to.
The Introverted Feeling Type
The extraverted feeling type
attaches her feelings to the people and things around her, but the introverted feeling type tries to be in rapport with her inner world, whether it be of psychic images or ethical and spiritual values,
and she tries to intensify this inner accord and embrace this world more deeply and fully. For the introverted feeling type the people and things around her are occasions for her feelings,
which flow inward and go deeper and try to become more intense and concentrated.
Because of the direction of her feelings she is often accused of not having any. She has a feeling, then that feeling immediately travels to her inner world, she weighs it on her interior feeling scale,
and only once the round-trip journey has been made can she express herself. So much inner activity is going on that she tends to keep her face and body still. People often overlook this type,
or are quick to classify her as slow. If we could have an exterior picture of what is really going on, however, we would be astounded. She lacks spontaneity not only because she is an introvert,
but because her feelings are a constant involvement for her.
It was a peaceful afternoon and a neighbor came over to chat with Betty and her mother. She casually mentioned that a neighborhood dog (the one Betty had spent hours with in happy contentment) had died. Betty froze. Her heart felt as though it had been pierced,
but she showed no outward sign of her inner turmoil. At long length the neighbor ambled off,
Betty rushed into the house, and in the solitude of her own room, she broke out into racking sobs. Her beloved friend was gone.
The introverted feeling type tries to protect herself against too strong an influence coming from the outer object and
detach her feelings from it so that they can travel within. Her clinging to inner values, silent as it is, can provide a good example from an ethical and moral point of view. People around her sometimes sense this inner reality, and fidelity to inner values. But at other times they sense how they are somehow being
treated with a certain reserve, held in check and subtly devalued.
The second and third functions of sensation and intuition can help her perceive her inner values. Her third, more extraverted function helps her come to grips with the outside world.
The introverted feeling types can be literally bursting with feelings but have no ready way to communicate them both because of their direction and because their content is not readily explicable in everyday terms.
Extraverted thinking is her weakest function. If she has a conversation, for example, she might spend hours, or even days,
still thinking up answers she could have given but didn't. Though she might really care for someone, that person might remain in the dark
because she cannot express herself well.
She is easily tripped up by a thinking type who overpowers her with his words. When this happens she gets overwhelmed and can no longer respond. If you show displeasure or impatience with her, she is totally lost and her introverted feelings block up her weak thinking power,
and she can easily be made to feel inadequate in our more verbal, active society. When upset, she will give you dark looks but it might be days before you know what is bothering her. Her fourth function thoughts are like birds - they come and go, and often fly off before they can be caught.