While the purpose and meaning of bells varies widely among different traditions, it’s generally recognized that the ringing of a bell communicates a message of some kind whether to participate in religious beliefs or to entities in the spirit world. It’s for this second purpose that the altar bell is used in Wicca. Some people refer to it as a “witches bell” to distinguish it from bells used for other purposes. A more old fashion term you may come across is “devil driver”.
The clear healing tone of the bell or bells can have a few different effects. The bells vibrations can banish unwanted spirits, and/or negative energies, call in positive, desired energetic influences, and/or simply clear stagnate energy in any space throughout ones home.