Electricity runs through the filament. Because the filament is so thin it offers a good bit of resistance to the electricity, and this resistance turns electrical energy into heat. The filament literally incandesces because of the heat. The problem with incandescent light bulbs is that the heat wastes a lot of electricity. Heat is not light, and the purpose of the lightbulb is light, so all of the energy spent creating heat is a waste.
Incandescent bulbs are therefore very inefficient.
They produce perhaps 15 lumens per watt of input power. A fluorescent bulb uses a completely different method to produce light. In a fluorescent tube there are electrodes at both ends of the tube and a gas containing argon and mercury vapor within the tube. These electrons bump into the mercury atoms and excite them. As the mercury atoms move from the excited state back to the unexcited state, they give off ultraviolet photons.