Ectomorphs are long and lean, with little body fat, and little muscle. They have a hard time gaining weight, as Fashion models and basketball players! Yeah, most of us love to hate these genetically-blessed individuals.
Mesomorphs are athletic, solid, and strong. They're not overweight and not underweight, so they can eat what they want without worrying too much about it. They both gain and lose weight without too much effort. Blessed either!
Endomorphs last but not least, have lots of body fat, lots of muscle, and gain weight easily. The endomorph has a relatively large body and short arms and legs. They may have more muscle than either of the other body types, but they often struggle to gain it without significant amounts of accompanying body fat. If you ever feel like you gain 5 pounds simply walking past a donut shop, you may be an endomorph!