Glowworms and fireflies are the same thing because they are the same species.
Glowworms are the larvae of fireflies and, in some species, the flightless females.
The larvae take one or two years to develop before passing through a brief pupal state and becoming adults. As larvae, they eat earthworms, snails, and the larvae of other insects, killing their prey by injecting poison into them.
After all that buildup, the adults, now fireflies, live for only five to thirty days. Adults eat nectar from flowers or, in some species, nothing at all. However, females of other species are cannibals.
All 1,900 species of glowing insects are members of the family Lampyridae, which is a pretty good name for a bug that lights up the night.
People have long held up insects as beautiful and commendable things, while at the same time crushing, poisoning, swatting, and cursing them.
Why bugs even waste their time on us after all that is hard to understand.