Chlorophyll is a chemical pigment, it is in the leaves of plants, leaves are full of this tiny stuff which are molecules of green color. Chlorophyll is the pigment that comprises chloroplasts, which are the structures or "organelles" responsible for converting the sun's energy into useful energy for a plant.

In plants, chlorophyll absorbs everything but green light, that is why we see it green, because the rest of the colors of light have been absorbed and only the green color is reflected and it is the color that reaches our eyes.

Chlorophyll is made inside the chloroplasts of plant cells through a series of chemical reactions. It is made from glutamate (a common molecule that is found in proteins in every organism on Earth) and other molecules found in the cell. The final product is a large ringed structure that is very good at absorbing light, which is what makes chlorophyll so special.

The following link takes you to a nice picture (the second picture from the top at the right of the page). Seen through a microscope, chlorophyll is concentrated within organisms in structures called chloroplasts – shown here grouped inside plant cells. Link.