Photosynthesis is a process carried out by an organism in which light absorbing pigments chlorophyll, carotenoids and xanthophylls are present which help in the reduction of $CO _{2}$ and oxidation of water.
$6 CO _{2}+6 H _{2} O \rightarrow C _{6} H _{12} O _{6}+6 O _{2}$