What are trilobites and what geologic era are they from? what does a trilobite look like

Well Trilobites first appeared about 521 MILLION years ago, which is around the Early Cambrian Period. Trilobites were early anthropods that lived in the Earth's sea. They had hard-shelled bodies, and their bodies were composed of multiple body segments and jointed legs. Trilobites are made up of 3 main body parts, the Cephalon (the head), a segmented Thorax, and a Pygidium (the tail). Hope I helped!