Green plants have the ability to make their own food. They do this through a process called photosynthesis, which uses a green pigment called chlorophyll. ... Chlorophyll's job in a plant is to absorb light—usually sunlight. The energy absorbed from light is transferred to two kinds of energy-storing molecules.
The s stands for the phase of that element or compound. The phase solid is represented by (s). In this problem it is saying solid sodium (Na) is reacting with Bromine (Br) gas to form sodium bromide.