Indoor gardens often have very little exposure to the sun, unless you've found the perfectly placed window for hours of sunlight during the day. Grow lights, or plant light bulbs ensure your indoor garden plants receive the light they need any time of day.
I've found
compact fluorescent light bulbs to be the best bet for indoor gardening. Plants react positively to the extensive range of color temperatures, and especially full spectrum plant light bulbs. Compact fluorescents are excellent for grow lights for various reasons, one of the foremost being the very low heat generation. All manner of plants, from seedlings to mighty (but mini) bonsais soak up the light and thrive.
You must take care in your implementation of compact fluorescent grow lights, or you can end up wasting energy and light. Inappropriately aimed plant light bulbs are not only wasteful, but the lack of light is definitely harmful to your plants. With poor implementation, you will at best have far more light bulbs than is necessary. There are also
fluorescent tube plant lights, but I'll focus on compact fluorescents here.
Positioning of the grow lights is integral to successful indoor gardens. There are several ways to aid the plant light bulbs in maximizing their efficiency. Adding a reflector is the most simple and effective thing you can do. Consider also that standard compact fluorescent light bulbs provide 360 degrees of light, but only a portion of that (90 degrees) will provide the light intensity your indoor garden plants need. Reflectors help focus that light directly where you need it. Think about getting multiple wattages and color temperature grow lights and plant light bulbs so you have the right bulb for every part of the growing process.
A final tip would be that because compact fluorescent light bulbs produce such low heat, you can and should place them close to the plants. You want the best light penetration you can get, and the closer the light bulb is, the better the penetration. This is a good primer for beginning knowledge of indoor gardening, but it's certainly not everything you need to know. The web has tons of info and tips on just this subject; when you know all you need to know and are ready to get some light bulbs, come on back!