Here is what an MR-16 LED retrofit bulbs looks like. This is the most popular and widely used type of light. This is a three LED light and uses 4.5 watts. The light puts out the same amount of light that a incandescent 20 watt bulb would emit. This particular light has a 60 degree spread and and is rated at 2700K. The K next to the 2700 stands for Kelvin Temperature Scale. Most lights will be in the 2700-3000K range of the Kelvin scale.
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The Kelvin Temperature Scale scale measures the color range of the light emitted by bulbs. The lower 1500K end of the range is very warm white while the mid range 4000K and becomes more of a white light. Above 4000 you start to get into more of a pure white or cool white color spectrum that is clearly generated by an LED light. You tend to see the pure white or cool white color spectrum more in some types of holiday lights