Step voltage electric shock             

When a phase of electrified device is grounded, the grounding current flows into the earth, showing different potentials at different points on the surface from the ground point. When a person simultaneously steps on two points of the ground surface with different potential, it will cause a step voltage shock. 

Phase-to-phase electric shock

When the human body is insulated from the earth, human body are simultaneously contacted two different phase lines or the two charged parts of different phases of the electrical equipment. Then current flows from one phase to the other through human body and form a closed loop. This situation is called phase-to-phase electric shock. 

Fatal current 

The minimum current that is life-threatening in a short time is called lethal current. In the case of the current not exceeding 100 mA, the main cause of electric shock is that the current causes ventricular fibrillation or suffocation.