A caterpillar is a young butterfly or moth that has just hatched out of its egg. A caterpillar is a kind of larva. When it is older, the caterpillar will turn into a pupa (also known as a chrysalis), and then later the pupa will turn into a butterfly.
Caterpillars usually have three pairs of small, but noticeable, true legs at the front and up to 5 pairs of fleshy false legs at the back.