What You Think Guys?
In above image as long as the tap is closed the water pressure is considered as VOLTAGE.
When a tap is open and water starts flowing, that is the point where CURRENT comes into the picture.
From above explanation, you can draw the following conclusion.
Voltage: Water pressure in the tank.
Current: Water flowing through a pipe.
When you touch a point which is at high voltage your body act as a pipe or a medium causing that voltage to go into the ground. Now here, what is flowing through your body is no longer voltage but current. So due to this, your body gets burned inside out and here culprit is current which causes your death.
The signs are to warn you that you should not present yourself as a PIPE and make that voltage to go into the ground.