Here's why:

* ATP stands for Adenosine Triphosphate. This molecule has three phosphate groups attached to an adenosine molecule.

* High-energy bonds: The bonds between these phosphate groups are called phosphoanhydride bonds. These bonds are high-energy bonds, meaning they store a significant amount of energy.

* Breaking the bonds releases energy: When a phosphate group is removed from ATP (to form ADP, or Adenosine Diphosphate), energy is released. This released energy can be used to power various cellular processes, such as muscle contraction, nerve impulse transmission, and biosynthesis.

In short, the energy stored in ATP is like a compressed spring. When the spring is released (the phosphate bond is broken), the energy is unleashed to do work.