what is the meaning of e=mc(square)?

E = mc^2 is popularly known as Einstein's Theory of
Relativity.  Although he did not come up with the formula, he was the first scientist to
put it to practical use.

E = mc^2 is mass-energy
equivalence.  E is for energy, m is for mass, and c is the speed of light in a vacuum. 
The speed of light (c) is a constant 299,792,458 miles per second.  Energy and mass
vary, depending on the object.

Mass-energy equivalence
means that an object has the same amount of energy regardless of motion.  Keep in mind
that an object that is not in motion has potential energy, while an object in motion has
kinetic energy.  As the speed of an object increases, the mass decreases and the energy
increases at an equivalent ratio.

The basic goal of
mass-energy equivalence is mass conservation and energy conservation.  Nature is
designed to waste nothing.  Energy can neither be created nor destroyed.  It only
changes form.  Following this line of logic, you can determine that mass also can
neither be created nor destroyed.

A prime example of E =
mc^2 is a nuclear reaction.  When two hydrogen atoms are united through fusion,
resulting in a helium atom.  The resulting helium atom has less mass than the two
original hydrogen atoms.  Thus, the missing mass gets converted into energy.  This
concept is also demonstrated through the thermal energy of the sun.  Hydrogen is
continuously being changed to helium through the process of fusion.  The energy is
released to warm the earth, and the mass of the sun is compensated by generating more
hydrogen.