Step 4: What does all that DO - How does a fluorescent light work, anyway?
The picture shows a simplified fluorescent tube and ballast. You'll notice that the ballast is an inductor. This is because an inductor can act as a current limiter 'for AC current without actually using up any power the way a resistor (as used for LEDs) would. A neat trick. The current through the inductor (and thus the lamp, since it's a series circuit) is proportional to the AC frequency, and the inductance of the inductor. If you've ever seen the magnetic-only ballast from a standard fluorescent light, you'll have an idea how large an inductor is required at the 60Hz AC that comes out of the wall.