Butterflies are insects - that means they have three body parts, six legs and wings as adults. They have an exoskeleton and that means their skeleton is on the outside.
Butterflies have a complete metamorphosis (remember that is the science word for change) going from an egg to a larvae (caterpillar) to a chrysalis and finally to an adult butterfly.
Butterflies eat nectar as adults. They have a long proboscis (tongue) that is hollow. They slurp up the nectar from plants. As larvae they also eat plants but as babies they eat the leaves of plants.
Butterflies can fly as fast as 12 miles per hour. While that may be faster than I can run, the fastest human being can run about 22 miles per hour.