Two types of work , external work of work by E-field.
A charge( can be positive or negative) experiences a force F to the right (due to E field).
If charge move opposite to the direction of this force , work has to be done as the charge is moving against this electric force. This work is done by external agent.
If the charge were to move in the direction of this electric force, work is done by the electric field.
The result of this two movement produces different type of energy. The first case where work is done by external agent against electric force will be stored as increase in electric potential energy. Most likely that there is loss in kinetic energy and increase in potential energy.
The second case where work is done by the electric field will be converted to kinetic energy. You may even say there is a loss in electric potential energy and increase in kinetic energy.
A positive charge moving from a pt of higher potential to a lower potential means a loss in potential energy.
A negative charge moving from a pt of lower potential to a higher potential means a loss in potential energy.
