I realized today that I have heard this equation my whole life but I have no idea what it means. I looked it up today. This was Einstein’s formula that he came up with in 1905. I wonder why it is so popular? Why is it the one equation out of many that is part of our pop culture? Because it is related to the atom bomb.
In physics, mass–energy equivalence is the concept that any mass has an associated energy and vice versa. In special relativity this relationship is expressed using the mass–energy equivalence formula
where

 E = energy,
 m = mass,
 c = the speed of light in a vacuum (celeritas),
 and the superscript 2 indicates the squaring of the c.