Question

What does nonpolar mean

Answer 1

read about polarity.do know what is polarity?

Answer 2

Non-polar bonds are bonds in chemical compounds where the difference between electronegativity is less than 0.4.
For example, methane is formed by non-polar bonds.

Other view can inspect the way we see the molecule from outside. Water, for example, has hydrogens on one side and oxigen on the other. Therefore we can say where it has + (H) and where it has negative side (O).
On the contrary, methane has evenly distributed carbon and hydrogen atoms, so it appears neutral from the outside.
Non polar compounds can't serve as electrolyte, neither they can be electrolysed.

Also, read wikipedia: http://en.wikipedia.org/wiki/Chemical_polarity#Nonpolar_molecules