A child once answered the question, "What is a skeleton?" this way: "A skeleton is a person with the inside outside and the outside off." So maybe we can describe a bug like this: "It's an animal with the inside outside and the inside in." Bugs are all characterized as "exoskeletons" - their skeletons are on the outside. This exoskeleton is made of a hard substance called "chitin" which provides protection for the bug's inside and prevents the bug from drying out. This exoskeleton is divided into jointed segments, each of which has pairs of appendages like legs, wings, antennae, etc. In fact, bugs tend to be pretty flexible because they are full of joints. Scientists call the whole bunch of them "arthropods", because their legs, "pods", are jointed, "arthro". Bugs are pretty small so it's hard to get a refined picture just by looking at them, but you can get a better idea about their joints by looking at some of their cousins like crabs and lobsters. A lobster is jointed all over, not just the legs, but the whole body, as well as their antennae.
Most bugs are jointed in their bodies too. And their bodies are divided into three parts: head, thorax, and abdomen. The majority of them have their thoraxes divided into three parts as well, each having a pair of legs and a pair of wings on the second and third parts of the thorax.
Their heads sport a pair of antennae, jointed, of course, and two sets of eyes (at least), one set being a pair of bubbles made up of many eyes. And naturally a mouth, which has jaws moving sideways, not up and down.
Complicated! Yet so small! And so old! Way more than six thousand years old. More like 350 million years! Man has been walking the earth only a small fraction of that time.
And many! God must certainly love bugs because He made so many of them. There are about 900,000 species of them that are known and probably three or four times as many yet unknown. They make up about 80% of all living animals. But they aren't everywhere. Not in the deep oceans and hardly any in polar regions or in hot springs. But I think we all agree: there are enough.
But where they are, they are everywhere! Being so small, they can exploit and often take over many nooks and crannies ("niches") in the forest, the jungle, the basement, the garage, the pantry, the bed, etc.
That's the bug, overall. But there's a lot, lot more. And then many different kinds. And oh yes! The Butterfly!