WHAT ARE YOU ?

Personality type theory aims to classify people into distinct CATEGORIES. i.e. this type or that. Personality types are synonymous with "personality styles".
Types refers to categories that are distinct and discontinuous. e.g. you are one or the other. This is important to understand, because it helps to distinguish a personality type approach from a personality trait approach, which takes a continuous approach.
To clearly understand the difference between types and traits, consider the example of the personality dimension of "introversion". We can view introversion as:
A personality type approach says you are either an introvert or an extravert
A personality trait approach says you can be anywhere on a continuum ranging from introversion to extraversion, with most people clustering in the middle, and fewer people towards the extremes

Somatotypes - William Sheldon, 1940's
William Sheldon (1940, 1942, cited in Phares, 1991) classified personality according to body type. He called this a person’s somatotype.
Sheldon identified three main somatotypes which is :

Endomorph [viscerotonic]

• relaxed, sociable, tolerant, comfort-loving, peaceful
• plump, buxom, developed visceral structure

Mesomorph [somatotonic]

• active, assertive, vigorous, combative
• muscular

Ectomorph [cerebrotonic]

• quiet, fragile, restrained, non-assertive, sensitive
• lean, delicate, poor muscles