Beetles have kept their primitive mouth parts, designed for chewing abundant solid foods. Many other orders have mouths fit only for more specialized meals, e.g., sipping sap. Tiny shingle-like scales cover the wings and bodies of most. Moths spin cacoons, butterflies spin a chrysalis. At rest, moth tends to fold its wings like a tent, while the butterfly presses them together overhead.
Moths are more subtly colored and fatter bodied than butterflies.
Moths tend to be more nocturnal than butterflies. Note the familiar wasp waist, where one segment of the abdomen is pinched in. Also the thin, transparent wings, hence the order name. A lot of our worst enemies here. Many also have tubular mouths for sucking and can transmit diseases, e.g., malaria, sleeping sickness, filariasis, yellow fever.