ATP is often referred to as the fuel of life, as it powers nearly all processes in living organisms. It enables your muscles to contract, your heart to beat, your brain to think, your nerves to transmit signals, and more. In essence, ATP is what keeps you active and alive.
ATP, or Adenosine Triphosphate (also known as Adenosine 5′-triphosphate), is a molecule that stores energy in its chemical bonds. This energy is released when cells need to perform work, such as when muscles contract during exercise. ATP is stored in your cells, ready to be used whenever needed.
ATP is synthesized from the foods we eat, especially carbohydrates and fats. The energy (calories) contained in our food is then stored in chemical bonds (high-energy bonds) in the ATP molecule. This transformation of energy occurs mainly in our mitochondriaMitochondria are ATP factories. They make most of the ATP in your body, mostly from glucose (sugar) or… More in a process called oxidative phosphorylationOxidative phosphorylation is the process by which ATP is formed by the transfer of electrons from NADH or… More.
When a cell in our body needs energy, these high-energy chemical bonds are split (hydrolyzed) and the energy is released. When this happens in a muscle cell, work is produced in the form of mechanical energy, and the muscle contracts.
There is much more to say, but I keep it simple. If you want to know more, please read the relevant articles on Wikipedia (Adenosine triphosphate and ATP hydrolysis) or check out the extensive scientific literature on this subject.