the method of turning functional stackups to four-letter names is as follows

discarding the first and last for a second, the middle two (for instance, ST in ISTJ) represent Perceiving and Judging functions. this a rule - you will never see ITSJ, as this is just how types are written. Perceiving first, Judging second, no matter which is dominant/auxiliary. but on that note, those are the top two functions, the two most prominent, so they will appear in the acronym. the bottom two functions will not appear in the acronym as they do not influence the type as much as the top two do. (of course all functions have a great influence though.)

next is the J/P preference. faggot internet sites be like, "you're judging so you're a J, you're perceiving so you're a P" or more rationally "you are a P so you prefer to perceive before you judge" but the former is just stupid, the latter only applies to extroverts, because the J/P preference only lets you know which function you use on your OUTER world: Judging or Perceiving, meaning which of the two functions in the middle of the acronym (ex. ST) is *extroverted*. if you're an STJ, i know your Thinking is extroverted (Te), because having a 'J' at the end means you use the Judging function (Thinking) extrovertedly. so if you're an ESTJ, you *do* prefer to Judge before you Perceive (note: Judge meaning make decisions, not necessarily negatively connotated) because you *prefer* extroversion, as indicated by the E.

so that's where I/E preference comes in. being an "introvert" just means you naturally prefer your primary introverted function over your extroverted one. the opposite goes for the extroverts.

so, if you are an STJ, i know your Thinking is extroverted, which means your Sensing is introverted (if you wonder why it cannot be both extroverted or both introverted, there must be *some* preferred method of going about the outside world, and some of the inside. you cannot be a double introvert, as that implies you have no outside world. jung made the same mistake at one point.). so all i need to know after i have 'STJ' down is if you more naturally prefer your Sensing or your Thinking. for an ESTJ, Te is the function they have relied on since childhood, and their most favoured function. for ISTJ, that's how Si serves them, and their Te is not as well-rounded or developed. must be honed.