I'm pretty sure the answer is that the normal boiling point means the substance is under "normal" or standard conditions. So the boiling point of the substance at a pressure of 1 ATM or 760 torr...
The melting point is where matter changes from a solid to a liquid- in the case of water, 32 degrees F at ambient pressure (1013 hPa). Boiling changes liquid to a gas- in the case of water, 212...
If the temperature of a liquid is less than its boiling point then the average kinetic energy of the particles in the liquid will be less than the energy required to escape the liquid. However,...
The melting point is the tempeature at which a solid turns to a liquid state. The boiling point is the temperature when the liquid turns to a gas or vapour.