The average Albedo for the planet Earth including its atmosphere is 30%
Albedo is the proportion of the radiation that is reflected by a surface. It is the measure of the reflective nature of an object means how reflective a surface is. The more reflective a surface is the higher the albedo value. Dark colour objects absorb most of the solar radiation and hence have a low albedo, whereas light-coloured ones have a high albedo, as they reflect most of the radiation. Ice and white clouds have high albedos. Albedo is also affected by Emissivity of an object. When electromagnetic radiation is incident on a surface, it is either absorbed causing the surface to get hot or it is reflected. The ratio of reflected to incident radiation is called Albedo.
Reflectivity: the percentage of incident light or solar radiation that is reflected.
Emissivity: the rate at which absorbed energy is radiated from an object. It is the ratio of the energy radiated by an object to the energy radiated by a black body of the same temperature.
0 to 1 scale (or in percentage): 0, corresponding to a black body that absorbs all incident radiation. 1 corresponding to a body that reflects all incident radiation. The albedo for the average snow surfaces is 90% (0.9) since it reflects most of the radiation incident on it. On the other hand, a dark concrete surface has a low albedo of 10% (0.1).