They're like regular fluorescents, but smaller and twisty-er!
A compact fluorescent light bulb, known more frequently as a CFL, is a fluorescent bulb that has been compressed into the size of a standard-issue (read: general use) incandescent bulb. The traditional long tubes of fluorescent lights have been twisted and turned into a condensed form to create the iconic CFL, and a CFL works in much the same way as its predecessor: producing an electric current that is driven through a tube containing argon and a small amount of mercury vapor, UV light is generated when power is switched on in a process which excites the fluorescent coating within the tube, emitting visible light. The entire process can take anywhere from 30 seconds to a few minutes to reach full brightness, which is why these kinds of bulbs take longer to "warm up" than regular incandescents or LEDs (which are instant-on). CFL bulbs typically last 6x as long as traditional incandescent and use, at most, a quarter of the power.
Did You Know?
Like a standard fluorescent bulb, CFL bulbs contain mercury and, as such, should be handled with care.
Light Bulb Moment
DON'T PANIC! While you should always exercise caution when handling light bulbs of any kind, the hazard associated wtih CFL bulbs may have been inflated beyond reason simply because of their relationship to a standard fluorescent tube. In 2008, an article featured in the scientific journal Environmental Health Perspectives touted that CFL bulbs contain about 3-5mg of mercury. This is roughly 0.01% of the mercury content found in those old, antiquated thermostats from wayyy back when. Further research shows, too, that only a minuscule fraction of that 3-5mg within a CFL is actually released when a bulb breaks. So! Please handle with care, and dispose of your bulbs properly (use a recycling service, such as one of the programs offered by GoodBulb here), but there is no need to wig out about poisoning yourself or your family with mercury should you drop one on the floor. Whew!