Like Indigo said, there is a lot of information and many concepts to take in. It might all seem overwhelming at first, but as an INFJ you'll probably have a natural curiosity for psychology systems, and if you stick with it you will have many of those 'aha' moments as it all becomes clear.
Several things to start you off.
These personality types are based on the work of Carl Jung, who determined that the mind has distinct cognitive functions: Feeling, Thinking, Intuition, and Sensing.
Feeling is reasoning based on philosophical and emotional judgments.
Thinking is reasoning based on logical and relative concepts.
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Ntuition is processing information through pattern recognition.
Sensing is processing information through sensory observation.
Each of these four functions also have a macro and micro perspective, called extroverted and introverted respectively. For example, Thinking is logical and rational. Introverted Thinking is concerned with the small picture, how things work at their inner most. Extroverted Thinking is concerned with the big picture, how things relate on an overall scale.
Therefore, there are 8 distinct cognitive functions (abbreviations in parenthesis): Extroverted Feeling (Fe), Extroverted Thinking (Te), Extroverted Intuition (Ne), Extroverted Sensing (Se), Introverted Feeling (Fi), Introverted Thinking (Ti), Introverted Intuition (Ni), and Introverted Sensing (Si).
In time you'll come to understand what these mean in much greater detail. For now, understand that everyone has and uses all 8 of these functions. However, everyone also has a favored preference in which they use these functions - a starting place, and an ending place. The order in which we prefer to use our functions is what creates our personality types.
INFJs prefer to start with Ni, then move to Fe, then Ti, then Se, and so on. This means we prefer to start our cognitive process with Introverted Intuition, which is the function of pattern recognition. From there, we use our Extroverted Feeling, our desire to care for and relate to others. After that, we concern ourselves with how things work by using our Introverted Thinking, and finally we take in the world around us as it is in the moment with Extroverted Sensing.
All of our functions support the ones before them. For example, our desire to care for and relate to others supports our pattern recognition, and our curiosity for how things work is usually used to support our desire to care for and relate to others, etc.
Every personality type in this system, 16 in all, are based on their own order of the 8 cognitive functions. For example, ISTPs have the following order of functions: Ti, Se, Ni, Fe, or expressed in long form, Introverted Thinking, Extroverted Sensing, Introverted Intuition, Extroverted Feeling, etc. The ISTP personality type shares a lot of the same function preferences with INFJs, just in a different order.
Now that you understand the basic concepts, we have a thread full of very helpful links for INFJs
here.
The one thing that is most important to understand is a quote Carl Jung himself. 'Every individual is an exception to the rule.' No one is going to fit a mold with this system. The human mind is too fluid and adaptive to compartmentalize neatly. These theories are based on tendencies, trends, and commonalities. For the most part, these theories are sound, so long as you understand that they apply to the big picture of all the people in the groups of personality types that comprise them, not to specific individuals with those personality types. There are going to be things about you that aren't perfectly typical of the INFJ description. That's very normal. We come in an array of variations. This is a science of tendencies, not absolutes. It is a system designed to expand upon the similarities, not the differences. If you keep these things in mind, all of this will make a lot more sense and be much more viable for you.
Welcome aboard. I hope you find this stuff as interesting as we have.
