Electrons are negatively charged elementary particles. They form the shells around atoms and ions. This or something similar is what you will find in text books. Soon, however, this information may have to be supplemented.
The reason is that many physicists believe that electrons have a permanent electric dipole moment. An electric dipole moment is usually created when positive and negative charges are spatially separated. Similar to the north and south poles of a magnet, there are two electric poles. In the case of electrons, the situation is much more complicated because electrons should not actually have any spatial dimension.
To read the rest of the article, click here.