Chlorophyll is a green pigment in the chloroplasts of plants and is a part of photosynthesis. In photosynthesis chlorophyll B comes before chlorophyll A.

Chlorophyll B helps chlorophyll A. It absorbs green light and it can absorb more light than chlorophyll A. It also collects the energy from the sun and passes it on to chlorophyll A.

Chlorophyll A absorbs blue-violet and red-orange colors and it reflects of green light. The two aren't too different, but they are different enough to have two major roles in the photosynthetic cycle.

Chlorophyll A and B are slightly different in that they absorb different wavelengths of light. Chl B is more useful in lower light situations and so there is more Chl B in shade-adapted plant cells. There are also different ratios of A and B according to the amount of a given Photosystem used in Photosynthesis by a given plant (There is Photosystem I and Photosystem II).