Personality is the combination of characteristics or qualities that form an individual’s distinctive character. Now question is how many factors describe personality completely? Psychologists differ on number of factors.
Hans Jürgen Eysenck believed that three factors extroversion, neuroticism and psychoticism were sufficient to map a personality. He designed Eysenck’s Personality Inventory to study personality. Raymond Cattell on the other hand came up with sixteen personality factors to describe a personality completely, he designed 16 personality factor questionnaire or 16 PF inventory.
Psychologists Paul Costa and Robert McCrae came up with five factors which they believe are sufficient to map a personality. These five factors are extraversion, openness to experience, agreeableness, conscientiousness and neuroticism. They designed NEO personality inventory for this.
Psychologist Robert Hogan came with his own version of five factor test called Hogan Personality Inventory. He made two changes in five factor model. He split openness to experience into two factors- inquisitiveness and learning approach, he also split extraversion into two factors- ambition and sociability.
All above psychologists belong to traits school of personality. Personality according to them is collection of traits. Traits are durable characteristics of a person ex. if you are introvert, then you are likely to remain so for long period of time, switching from introversion to extraversion is not easy.
Types are collections of traits that are said to occur together in some individuals. Some personality tests use types instead of traits to study personality. Most popular inventory studying types is MBTI or Myers–Briggs Type Indicator. Katherine Briggs and her daughter Isabel Myers designed MBTI based on research done by psychologist Carl Jung and which was published in his book Psychological Types. Jung was of opinion that people have preferred ways of perceiving and deciding. These were put in from of four dichotomies by Briggs and Myers, combination of these resulted into sixteen personality types.
Purpose of personality tests is to help person understand himself and use information to make improvements.
In case you are planning to use it for organisational purpose, it is better to go through manuals before finalising the test ex. MBTI is not supposed to be used for recruitment.