Light Spectrum - This refers to what spectrum the light being emitted is best used for. LED grow lighting comes in the following spectrums:

Full Spectrum - LEDs are designed with a mix of blue (veg) and red (bloom) diodes that emit an ideal spectrum for all stages of a plants life. Some full cycle LEDs have customizable spectrums like the KIND K5 series which allows you to turn up or down different sets of diodes to make your own custom spectrum.

Veggetative Spectrum - LEDs only use blue diodes which are primarily used during the early growth stages of a plants life. These are good for clones, seedlings, and the vegetative stage, but are not recommended to flower with.

Bloom Spectrum - LEDs use red diodes which are designed to be used during the bloom or flower stage of a plants life. Using bloom spectrum LEDs will help promote budding by signaling to the plant it is nearing the end of its life cycle and it is time to reproduce.

Learn more about LED lighting here.