NADPH is reduced NADP (Nicotinamide adenine dinucleotide phosphate). It is an electron carrier.
The molecule exists in two forms that vary in whether or not they are carrying electrons. NADPH is the reduced form the of the molecule (has electrons). NADP+ is the oxidized form of the same molecule (lacks electrons). NADPH is produced in cells primarily by reactions in the pentose phosphate pathway. In plants, photosynthesis is another source of NADPH. NADPH donates electrons to biosynthetic reactions.