An electrical dipole is a couple of two electrical charges identical in amplitude but opposite in sign, say +q and -q (q>0), separated by a distance d.

This is for istance the electrical model of polar molecules.

see also

http://en.wikipedia.org/wiki/Electric_dipole_moment

If you calculate potential due to a dipole at a distance which is

large compared to d, then leading term in the potential cancels

due to the presence of both +q and -q, but there is a sub leading

term in the expression for potential proportional to 1/r^2. Therefore

for a single charge electric field falls as 1/r^2 for dipole potential

falls as 1/r^2. Dipole potential, thus, falls off quickly and corresponding

electric field falls of as 1/r^3, which is even faster. Dipole interaction,

consequently, is a short distance phenomenon. This phenomenon

is manifested in nature at many places. A prominent place being

the interaction of two atoms, where each atom is a dipole and the

mutual interaction is a dipole-dipole interaction. This interaction is

thus very fundamental to our own existence.