See the section on Albedo for the basic definition. For the Moon, the average albedo for the solar spectrum across the lunar surface is 0.12 (i.e. only 12% of incident sunlight is reflected back, and the remaining 88% is absorbed). From the Apollo missions it's known that a substantial portion of this reflected light is sent directly back at the Sun, so we never see it from Earth. At the angles we can see the Moon appears even darker, with an effective visual albedo of 8% or less.
Individual features on the Moon have visual albedos that range from under 10% (the dark mare regions) to as high as 25-30% for bright ejecta and highland regions.
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