Residual haunting activity can occur when something traumatic/stressful occurs, such as a murder. Negative energy is released into the atmosphere, causing the events to imprinted or recorded, like a recording tape, it will play the events over and over again. The entities involved in this residual haunting activity are unaware of their surroundings. This is not an intelligent haunting, there is no interaction between you and the entity.
Residual haunting activity can also be caused by positive energy. Many times you have heard ghost stories, where people can hear the sounds of a party. They hear music, singing, dancing, laughter and when they enter the room where they hear the party, there is no one there. Residual haunting activity can be the specters of living beings.