Tutoring biology, you need to be aware of the connection between ATP and energy.

In a factory or a mill, there likely is a power plant where fuel is burnt en masse. The energy is captured there (often in the form of electricity), then channeled to the other locations as needed.

The human body, though, releases and consumes energy in a different way.  Each cell receives fuel (glucose), burns it internally, then captures the released energy by using it to synthesize a high energy chemical bond.  That bond can be broken at will when energy is needed.

ADP is adenosine diphosphate (adenosine bonded to two phosphate groups). When the cell burns glucose (in its mitochondria), the energy released is used to bond another phosphate to the ADP, so it becomes ATP (adenosine triphosphate).

When the cell needs energy, it breaks an ATP into an ADP and a phosphate.  The breaking of that bond releases energy the cell can use to power any life process.  Later, when the cell burns more glucose, it will use the energy to bond the ADP and the phosphate back into ATP.

The burning of one glucose molecule produces 36 or 38 ATP.

Hope this helps:)

Source:  Inquiry into Life, Eleventh Edition, Sylvia S. Mader.  McGraw-Hill:  2006.

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.