In Botany, the word for a herbaceous plant is herb (from Latin herba, "grass") but it is common to use the word herb only for plants that are used in perfumes, medicines and for cooking, even if they are not herbaceous plants.
Herbaceous plants may be annuals, biennials or perennials but most are annuals and die at the end of their growing season (the time when they produce flowers, fruits and seeds), leaving their seeds on the soil; those seeds will produce new plants with good weather. Wheat and pea are annual herbaceous plants.
Biennial and perennial herbaceous plants will live for two or more years but the stems that are in the air will die every year; the underground stems will form the new aerial stems (stems that are above the ground). Underground roots and stems can resist more the bad weather (winter or a very dry season) than leaves and stems that are above the ground. Bulbs are biennal and peonies are perennial herbaceous plants
Most herbaceous plants are small and their stems are not thick because they do not have much wood but there are some cases of big herbaceous plants. Bananas and papaya (a tropical fruit) are herbaceous plants but they look like trees; papaya has a thick stem but without much wood.
Herbaceous plants are the first plants with flower that come to live in barren lands (lands without plant life) because they are small and produce many seed. They are also found in places where the weather conditions are not good for most plants; they can use the little rain that falls in deserts, and they can get enough heat to grow where the soil is covered with snow and ice most of the year, like in very high mountains.
Herbaceous plant Facts for Kids. Kiddle Encyclopedia.