The classic three body or somatotypes are listed below, but many people are not just one specific category, but rather a combination of them. I'm not a huge fan of labeling people into such simple classifications, but I don't think it hurts to acknowledge one's basic body type.
Ectomorphs- These are people with thin frames who have a hard time gaining weight. One way people determine if you fit in this category is if you can put your middle finger and thumb around your opposite writs and have them touch or overlap.
Endomorphs- They have a tendency to be heavier and stockier than most people. Their metabolisms are typically slower and they gain weight more easily.
Mesomorphs- This fortunate group is naturally more muscular and have a more athletic build than the general population.
There are also body type classifications I hear women refer to such as apple, pear, or hour glass shaped. These are determined by where you carry your weight.
How much stock should we put into body types and shapes? It makes sense to address these differences when you are creating a fitness program. If you are a heavier person who gains weight easily then this should be addressed when you are talking about nutrition. It certainly makes sense to acknowledge your body type for how you dress and what kind of appearance you are trying to achieve.
Your body shape can also be an important factor when it comes to addressing health risks. Apple shaped people who carry excess fat on their abdomen as opposed to their legs and butt are at a higher risk for heart disease.
Many people's perceived ideal body image comes from Hollywood, models, or athletes, but very few people in the general population fit that description or have "ideal" proportions. It's easy to be dissatisfied with the genetics and predispositions we've inherited, but all kinds of body shapes and sizes can be beautiful. Think how boring life would be if everyone looked like fitness models.
Some people can work all they want, but a large framed woman may never look petite. As an ectomorph, I could spend my entire life in the gym and I would never look like a professional bodybuilder. The key is to take good care of your body and train and develop it to your own personal potential.