Complex sentence: In general, the albedo depends on the directional distribution of incident radiation, except for Lambertian surfaces, which scatter radiation in all directions according to a cosine function and therefore have an albedo that is independent of the incident distribution.
Split into simpler sentences: In general, the albedo depends on the directional distribution of incident radiation. Except Lambertian because they scatter radiation in all directions according to a cosine function and therefore have an albedo that is independent of the incident distribution.