This is from Gifts Differing, and I feel it is an excellent description of the differences between the two.
A good way to visualize the difference (between introversion and extraversion) is to think of the dominant process as the General and the auxiliary process as the Aide. In the case of the extravert, the General is always out in the open. Other people meet him immediately and do their business directly with him. They can get the official viewpoint on anything at any time. The Aide stands respectfully in the background or disappears inside the tent.
The introvert's General is inside the tent, working on matters of top priority. The Aide is outside fending off interruptions, or, if he is inside helping the General, he comes out to see what is wanted. It is the Aide whom others meet and with whom they do their business. Only when the business is very important (or the friendship is very close) do others get in to see the General himself.
If people do not realize that there is a general in the tent who far outranks the Aide they have met, they may easily assume that the Aide is in sole charge. This is a regrettable mistake. It leads not only to an underestimation of the introvert's abilities but also to an incomplete understanding of his wishes, plans, and point of view. The only source for such inside information is the General.
A cardinal precaution in dealing with introverts, therefore, is not to assume, just from ordinary contact, that they have revealed what really matters to them. Whenever there is a decision to be made that involves introverts, they should be told about it as fully as possible. If the matter is important to them, the General will come out of the tent and reveal a number of new things, and the ultimate decision will have a better chance of being right.