Bumble bees bring pollen to flowers so that the flowers can produce fruits, vegetables, nuts or other foods. A bumble bee might visit the flowers on a tomato plant, for example. When a bumble bee does that, the bee helps make sure there are going to be lots of wonderful tomatoes on the plant.
Scientists who study insects such as bumble bees are known as entomologists (sayEN-toe-mall-oh-jists). If you like insects, maybe you will want to be an entomologist some day.