Two light bulbs can both give out white light, but certain colours will not show up well when illuminated by the first bulb, while they look fine under the second bulb. This means the first bulb has a lower colour rendering index (CRI).
Traditional bulbs have a CRI of 100. A good CFL will have a CRI of 80 or more, which is good enough for normal domestic use. Most LEDs have a CRI of 90 or more, so are usually fine. However, if you buy bulbs with a CRI of less than 80 there is a risk that the quality of light in your home will look a bit odd.← What should I know about quality of light from the LED Lamp?