Butterflies and moths are close relatives so sometimes it can be tricky. Here are a few ways to sometimes not always distinguish between them:
Butterflies have clubbed or hooked antennae, Moths often have feathery antennae.
Butterflies are usually active during the day, Moths are more active at night.
Butterflies fold up their wings above their heads, Moths rest with their wings folded behind them.
Butterflies generally have more slender, hairless bodies, Moths generally have thick, furry bodies.
Butterflies have hard, smooth pupae without incorporating other biological material, Moths form a cocoon with leaves, twig, etc for additional protection and camouflage.
The Skipper family (Hesperiidae) of butterflies tends to be the most easily confused as moths due to their often dull colors, subtle patterns, and thick, hairy bodies.