Picture Source - By At09kg (Own work) [CC BY-SA 3.0], via Wikimedia Commons
Photosynthesis is a Process
Used by the Plants
To convert Sunlight energy (Or other lights energy)
Into Chemical energy.
This Chemical Energy is stored in Sugars (Carbohydrate molecules = C6H12O6)
And is used for fuelling the Organisms activities.
In other words as per equation below
When Light falls on Carbondioxide molecules and Water molecules,
these molecules get synthesized into
Sugar & waste product called Oxygen.
FORMULA FOR UNDERSTANDING PHOTOSYNTHESIS
6 CO2 molecules + 6 H2O (Water molcules) = When Light falls = Sugar + Oxygen (O2-Waste product)
Reference - https://en.wikipedia.org/wiki/Photosynthesis