AC shock vs DC shock
Universally two kind of energy source are available. One is AC source and another one is DC source. Simple overview about AC and DC.
AC => Alternating current, which alternates the direction of the current, AC has frequency.
DC => Direct current in Which the current flow in the same direction, the electron do not change its polarity. The source which has f=0 such source is called DC source.
In our case Which shock seviourly damages the human body. As we said in above the alternating current source has the frequency (repeating cycle). Due to the periodic cyclic action, at a point the alternating current through the conductor becomes zero. Hence there is no current the flow through the human body.
But in case, Direct current the current will in the same direction and flows constantly. It does not reach the zero point at any cost. Hence the current flow remains same.
Refer the diagram:
In AC shock the human can survive but in DC shock human can not survive.