Introducing yourself with four letters has become normal. What type systems reveal and what they hide.
Sorting people into a few types makes them easy to remember and easy to discuss. It helps start a conversation with someone new and gives you a handle when you lack words for yourself. Type systems spread because they are usable, not because they are accurate, and that in itself is not a bad thing.
Asking whether someone is introverted or extroverted assumes people fall into two groups. Measuring personality traits actually produces a distribution thickest in the middle and thinning toward both ends. Most people sit somewhere in between, and pushing them to one side discards information. That is also why someone near a boundary gets a different type on retesting.
Research tends to place people along a few dimensions by degree rather than sorting them into types. A widely used approach uses five dimensions. It is less memorable than a type name, but results move less when the same person is measured again.
The trouble starts when a type becomes the end of an explanation. Saying 'that is just my type' treats changeable things as fixed. The same applies to others: explaining someone by type removes any reason to look further into why they acted as they did. Types are useful as a starting point and lose their use as a conclusion.
Personality types are sometimes used to select or assign people, which is a far heavier use than the instruments support. Types can shift over time and relate only weakly to job performance. There is a wide gap between using something for self-understanding and using it to judge others.
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