Monkey Business Images/Monkey Business/Getty Images

In botanical terms, legumes are defined as plants belonging to the family Leguminosae, all of which share the characteristic of enclosing their seeds inside pods. When people speak of legumes as food, though, they're usually referring not to the plants but to their mature fruit -- beans and peas. However, the United States Department of Agriculture's food classification system categorizes immature peas and beans typically eaten fresh, including green peas, string beans and green lima beans, as vegetables.

Legumes: Pod-Bearing Plants

ruidoblanco/iStock/Getty Images

Among the most familiar fruits of thousands of existing varieties of pod-bearing legume plants are lentils, split peas, kidney, navy, pinto and black beans. Technically, peanuts aren't true nuts at all, but legumes. Legumes, which use nitrogen to manufacture protein, are among the most nutritious of all plant foods.

Forms of Beans and Peas

vovashevchuk/iStock/Getty Images

Some legumes such as chickpeas, aka garbanzo beans, and black-eyed peas can be eaten from fresh or frozen states with only light cooking. Others such as mung beans are often sprouted and added to salads. In grocery stores, most beans and peas are typically sold either in dried form or in cans, already cooked.

Pulses: Always Dried

SAKDAWUT14/iStock/Getty Images

One of the most valuable characteristics of many mature beans and peas is that they dehydrate naturally without attracting mold or losing nutritional value, enabling them to be stored almost indefinitely and rehydrated through cooking. Beans and peas in dried form are called pulses to distinguish them from those that still hold moisture.