The contribution of foods to nutrition has 3 categories: carbohydrates, proteins, and fats.
Fruits are rich in healthy carbohydrates. Other than potatoes, which are a near-ideal balance of carbohydrates and proteins, vegetables tend to offer abundant protein. Nuts and seeds offer healthy fats.
Seafood, especially fish, is extraordinarily rich in protein, as are eggs. Meat is a mixture of protein and unhealthy animal fat, as is dairy.
There are other essential nutrients, albeit in small quantities: vitamins and minerals. We begin with these, so that the described foods can be better appreciated for their nutritional qualities.
Vitamins are organic molecular micronutrients. In contrast, dietary minerals are inorganic elements which are combined into forms that are biologically useful. Both are nutritionally essential, albeit in tiny quantities.