What does this symbol stand for?

[Lorax]

4πε0r^2

Thats 4pi (backwards 3 0) R squared.

I forget what the backwards 3 o stands for can someone help me out

[Hurkyl]

\epsilon_0? Permeability of free space. (Or is it permittivity? I always forget which)

[Gokul43201]

\epsilon _0 is known as the permittivity of free space and is equal to about 8.85~
*~ 10^{-12}~~ F/m

It is a proportionality constant relating the electric displacement vector to the field strength.

OR, it can be thought of as a constant connecting electric field (or force) to the values of charge and distance.