In technical terms, Full Spectrum light is a board term describing light that covers the electromagnetic spectrum. Ranging from infrared to near-ultraviolet, as well as all wavelengths that are useful to plants and animals. Sunlight for example is considered full spectrum.
Human eyes respond better to artificial light which closely replicates the intensity and range of colours found in natural daylight. And Full Spectrum light bulbs and daylight bulbs do just that.
It has been noted that people who work under Full Spectrum light bulbs or daylight bulbs report feeling less tired, moody and experience reduced eyestrain.