The following is a brief description of the four preferences found in the MBTI. This post is essentially an exercise in synthesizing data, so I'm writing off the top of my head based on various readings and discussions that I've engaged in. Feel free to add to, or dispute, what I have described here.
The 4 Preferences
Extravert vs. Introvert (E/I): This preference is also called the attitudes and refers to the flow of energy.
For the longest time I thought this preference was all about enjoying being with people or wanting to be on your own. But it really has more to do with interactions with the outside world (the world around us that we can see, touch, etc.) and interactions with the inner world (imagination, thought, dreams... all that stuff that goes on inside us). An extravert is someone who draws energy from interacting with the outside world. That might involve lots of interaction with people, but it could also involve spending time outdoors, traveling, going to concerts... anything that involves interaction with something outside of the body. An introvert is someone who expends energy when interacting outside the body. The introvert needs time alone spent in reflection and thought. Whereas the extravert gains energy by interacting with physical things, the introvert restores energy by interacting with mental things -- concepts and ideas. An introvert who spends too much time dealing with the physical world will probably end up feeling drained. An extravert who spends too much time alone or in the world of the mind will probably end up feeling depressed.
Sensing vs. iNtuition (S/N): This preference is also called the perceiving functions and refers to the way information is consumed.
Have you ever had an experience where you and another person both saw the exact same event and yet you came away with completely different takes on what happened? You both experienced the same inputs, but somehow you both gathered very different information from the experience. In other words, your perceptions of the experience were different. The perceiving functions in the MBTI are all about how people gather and interpret information. Some people will look at a bunch of trees and see a forest. These people are intuitive, seeing the bigger picture based on a set (or subset) of data. Others will look at a bunch of trees and see a bunch of trees. These people are sensing, seeing the individual pieces of data as they are perceived by the senses. Intuitives tend to see patterns in data. From these patterns they are able to make predictions about the future. In general, intuitives are big picture people who often think to the future. Those with a sensing preference are often considered to be detail people. (Not that iNtuitives don't see details, but they're more likely to gloss over details, and once they get enough details to jump to an overarching view of the situation, or a metaphor or system that organizes the data, they'll leave the details and pursue the bigger picture that those details present.) In addition to being able to focus on the details, those with the sensing preference tend to appreciate anything that they can interact with using their five senses. How things look or taste or feel might be very important to them. The words sensing and intuitive can be a bit confusing, but I try to think of it this way. S's take in information through their senses. N's might take in some of that information, however their focus isn't on the things they sense, but upon what they can intuit from those things.
Feeling vs. Thinking (F/T): This preference is also called the judging functions and refers to the way decisions are made.
The words used to describe this function can also be confusing. For the longest time I thought those that used thinking made decisions based on logic and those that used feeling made decisions based on how they felt about things. But that's only half right. A better way to look at feeling is to think of decision making in light of seeking a harmonious solution (even if it's not the most logical solution). For those that use feeling, decisions are made based on relationships with others. Those using thinking base their decisions on data and may give little or not regard to how it affects people. Because of this, T's are often thought of as cold or uncaring, when that might not at all be the case. Someone can use thinking in making a decision with every intention of doing the kind or loving thing, but that won't be their criterion in resolving their decision, the logic of the situation being more relevant in their mind. It's also important to note that T's may use logic to come to a conclusion, but it might very well be a loopy form of logic that wouldn't hold up in my old geometry teacher's class. In the same vein, F's might make a decision based on how it will affect other people, but it might not be a decision intended to bring harmony at all, but discord. T's and F's can both be remarkably brilliant or excruciatingly dimwitted. How you make your decisions doesn't determine how "smart" you are. T's often look down on F's because their decisions seem illogical (and may very well be illogical), but that doesn't mean that they're not still brilliant decisions that are just what the situation called for. And F's sometimes look down on T's because they seem so unfeeling and detached, but likewise, that can also be just the kind of decision that a situation called for. Both means of making a decisions have value.
Perceiving vs. Judging (P/J): This preference doesn't have a name of its own as far as I know, but it has to do with a person's lifestyle and refers to the way a person relates to the outside world (or how they behave when they're extraverting).
If you glance back up at the S/N section, you'll notice that those were the perceiving functions. And if you glance at the F/T section, you'll notice that those were the judging functions. And now here we are looking at perceiving and judging. If you are a perceiving person, then when you extrovert (or when you relate to the outside world), you interact with your perceiving function (whether S or N). And if you are a judging person, then you relate to the outside world with your judging function (whether F or T). More on this in my next post on personality types. P's and J's tend to also have characteristics of their own, that I don't think are related to S/N or F/T. J's like closure. They feel a little uncomfortable when something is left hanging, unfinished or undecided. They're willing to forego additional information gathering in order to "just get this thing over with". P's, on the other hand, are much more willing to continue to gather information until they're quite sure they've gotten all the bases covered before they final settle down to make a decision. In fact, sometimes P's aren't comfortable making that final decision because they're not quite sure they've finished gathering information. Deadlines can help a P finally bring closure to a project. P's tend to be more spontaneous than J's who like everything scheduled or orderly.
This is just a cursory overview of the 4 preferences in the MBTI. You may look at a preference and say, "Well, this part fits me, but I'm not like that other part at all." Not everyone uses one preference all of the time. My mom is a strong S, but when she cooks, her iNtuition shines. She strays from strictly following recipes in a way that would make most S's cringe. But most of the time, she uses Sensing, so that's considered her preference. It's also helpful to think of these traits in terms of yourself left to your own devices. At work, or when trapped in family dynamics, or in certain social functions, we may feel that we have to behave in a certain way because that's what's expected of us. And we might be very good at behaving that way, but being good at something doesn't make it a personality type preference. The behaviors you would naturally gravitate toward when on vacation or during free time are often a better yardstick to use when trying to figure where you fit in.
And remember, these are amoral characteristics. None of this is about being right or wrong. When you figure out your personality type, it should be a wonderful means of self discovery and self affirmation. It's also a great way to see those niggling little things in others and realize that it's a result of their own personality type. Realizations like that help us to accept others more as they are and to stop trying to force them into a mold that fits us better than it does them.