I've done a fair amount of research on this topic and have used full-spectrum lighting in my office for the last 5+ years. Daylight when passed through a prism reveals that it is made up of the variety of colors found in the rainbow. Full spectrum light emulates this quality of light. Typical incandescent lighting--the normal lightbulb spikes as yellow--with none of the other parts of the spectrum. That's why on a winter night if you stand outside the house the light looks yellow coming through the windows. Halogen, also popular also spikes in the yellow range.
It was suggested that I post the specs on the lighting. Not all bulbs that claim to be natural sunlight meet these specs. Specifically, the CRI needs to be above 90. The CRI is a measure of how the light compares to actual sunlight on a vibrantlly sunny day in the summer. The closer to 100, the better--and also the more expensive.
Another way of measuring light is in degrees Kelvin, which I do not fully understand, but full spectrum is considered to be 5000K.
The specs on the light that WYSIWYG is using are:
Philips T 12 40 Watts, with an output of 2200 lumens with a CRI (the package says of 92 and 5000K. Prices vary, but these were about $7 each at the local Home Depot.