The word electromancer would mean a magician who employs electricity (much as a necromancer is a magician of death, or an oneiromancer is a magician of dreams). It is not a well developed category of magic.
The Electromancer was created on 1995-07-21.
Yes, Goblin Electromancer reduces the cost of X spells by reducing the generic mana cost of the spell by 1.
Some cards in Magic: The Gathering have abilities that reduce their casting cost. Examples include "Goblin Electromancer" and "Baral, Chief of Compliance."