A fluorescent bulb gets its light from mercury vapor inside a glass tube. The incandescent bulb — the kind associated with Thomas Edison — has a filament that glows when it's heated.
You can also use fluorescent to describe something that's so vivid and bright it seems to give off light. Fluorescent is related to the word fluorspar, or fluorite, which is a mineral that glows. Notice the -u- in these words. Fluorescent comes from the Latin fluere "to flow" — fluorspar can be added to welding compounds, for instance, to make them flow more easily. Florescent, without a -u-, means "flowering," from Latin flor-, which is a completely different root.