CFL stands for Compact FLorescent. They are marketed as energy efficient replacements for regular incandescent light bulbs. You can buy them pretty much anywhere light bulbs are sold. The packaging tends to have the actual watts in small letters and the "equivalent" wattage in large letters. Ignore the equivalent value. It's the real watts that you care about.
Most CFLs fit into plain, vanilla light sockets. The biggest CFLS (greater than 105 watts) usually require non-standared mogul fixtures.
The advantages of CFLs are:
- they are inexpensive
- they do not generate very much heat.
The disadvantages of CFLs are:
- They are less energy efficient than High Intensity Discharge (HID) lights such as High Pressure Sodium (HPS) and Metal Hallide lamps (MH). For the hobbyist grower, this is not a big deal.
- The light from CFLs does not penetrate through the plant canopy as well as HIDs do.
Growers employ various tactics to compensate for the lack of light penetration, including:
- Use many lower wattage CFLs positioned about the plant to provide even illumination rather than using a smaller number of more powerful lights.
- Train plants to grow short and wide rather tall and narrow. There is a sticky about Low Stress Training (LST) in the Absolute Beginners forum.
- Employ the Screen of Green (ScrOG) technique to create an even canopy of bud sites.
For vegetative growth, you want to use lights with a color temperature of 6500K (cool white). For flowering, you want to use lights with a color temperature of 2700K (warm white). But you can use a mixture and some people say that it is better to do so.
There is a sticky in this forum called Kamel's CFL Guide.
Good luck with your grow.