what is the difference between NADH and NADPH and also NAD+ and NADP+ ?

NADH is Nicotinamide adenine dinucleotide while NADPH is Nicotinamide adenine dinucleotide phosphate. Both these molecules are electron carriers and help in various biochemical processes.

Structural difference: The difference is only in the phosphate group. NADPH has a phosphate group while NADH does not have a phosphate group.

Functional difference: 

• NADH is involved in catabolic processes, where complex molecules are broken down to release energy. For example : Cellular respiration.
• NADPH is involved in anabolic processes, where complex biomolecules are synthesised from simple substances. For example: Photosynthesis

NAD+ is the oxidized form of NADH; while NADP+ is the oxidized form of NADPH.