There are a large number of persons live on this plant, and as it is known to all that there is no same person which indicate that these persons are undoubtedly differ to each other: race, religion, appearance, occupation, etc. Some people may says that there are some guys have similar interests and similar temper, and these similarites make them friend. Well, I admit that they must share some similarities to make them so , but I still insist they cannot be exact idtentical. In another word, the reason cause their similarity is partially determined by their personality, but people's personality cannot be exact the same, soI would like to elaborate a topic about a typical trait of person - personality, to describe personality at the broadest level in order to make sense why different people have different charateristic.
We can easily get that traits are organized hierachially, which named as "BIG FIVE" classify people's personality into fave aspects : A.Extraversion refers to behavior associated with positive emotionally and seeking new and exciting experiences, such as sociable, talkative, assertive, friendly versus silent, passive, reserved etc. B.Aggressive, indicate behaviors associated with early temperament and cooperation with others, such as sympathetic, kind, cooperative versus suspicious, difficult, untrusting, etc. C.Conscientiousness elaborate behaviors associated with constraint and longer life-span, such as organized, disciplined, dependable deligent versus careless, negligent, unreliable, etc. D.Neuroticism means behaviors assosiated with negative, emotionality and overreaction to strss, such as anxious, mood tense, vulnerable versus relaxedm poised, etc. E.Openness to experience refers to behaviors assosiated with liberalism and political attitude, such as imaginative curious, creative, unconventional versus unimaginationve, etc.
We can classify people into 5 groups in accordance with the five stages of personalities. As far as I am concerned, the persons who have the similar traits will have similar personalities which will induce similar interests, or similar behaviors. However, there is still another hypothesis that people's behaviors are shaped by the outside influnces, such as parental education, the surroundings they live in etc. we can not get the exact conclusion yet without valid evidence to say which one is correct.
There are some links about personality: