ATP is a nucleotide that contains a large amount of chemical energy stored in its high-energy phosphate bonds. It releases energy when it is broken down (hydrolyzed) into ADP (or Adenosine Diphosphate). The energy is used for many metabolic processes. Hence, ATP is considered as the universal energy currency for metabolism.
Its functions are for intracellular energy transport for various metabolic processes including biosynthetic reactions, motility, and cell division. It is also used as a substrate by kinases that phosphorylate proteins and lipids, and by adenylate cyclase to produce cyclic AMP.