It once denoted heretics and witches but can apply to others as well. In the early days of the Church to be excommunicated placed a person in a perilous position. The person was denied the Sacraments, the fellowship and protection of the Church, and often regarded as a social outcast which often led to drastic consequences. The rite is equivalent to a curse, and involves a bell, the Holy Book, and a candle. The excommunication ritual has presently lost the dreaded fear it once carried because the Church no longer holds the life and death power over people as it once did.
Most Protestants consider themselves excommunicated anyway.
The occultists and witches who the Church considers devil-worshipping reprobates no longer care whether they are excommunicated or not because many feel they are following the old and true religion of witchcraft.