special relativity - What can $E=mc^2$ do?

In the famous equation $E=mc^2$, the variables stand for:

$E$ is energy, $m$ is mass, and $c$ is the speed of light (in vacuum).

And I understand the equation fairly but limited in knowing in its effects/outputs in reality, honestly.

• Some example? Could anybody please give me some sort of examples in real world which are done by this equation?