Photosynthesis, generally, is the synthesis of sugar from light, carbon dioxide and water, with oxygen as a waste product.
It is arguably the most important biochemical pathway known; nearly all life depends on it.
It is an extremely complex process, comprised of many coordinated biochemical reactions.
It occurs in higher plants, algae, some bacteria, and some protists, organisms collectively referred to as photoautotrophs.
Most plants are photoautotrophs, which means that they are able to synthesize food directly from inorganic compounds using light energy - for example the sun, instead of eating other organisms or relying on nutrients derived from them.
This is distinct from chemoautotrophs that do not depend on light energy, but use energy from inorganic compounds.