These are practices of negative energy with the use of objects and symbols. Some of these objects and symbols can attract negative energy or can be connected to some negative energy.
Example 1: Burning the picture of a person in fire with the very negative intention to harm that person.
Example 2: Using symbols as form of invoking negative energy to harm someone.
Example 3: Tying strings and beads after prayers and keeping things in homes and personally for protection etc.
