Electric field, E, is the electric force, F, per unit charge. E=F/q’. Both F and E are vectors. The direction of the field is the direction of the force that would be exerted on a positive test charge. The electric field is radially outward from a positive charge and radially inward towards a negative test charge. The magnitude of the Electric Field does not depend on the test charge but on the charge creating the electric field.
If the test charge is positive, the vectors E and F point in the same direction. If the test charge is negative, E and F point in opposite directions.
An Electric Field Line is an imaginary line through space that, at every point is tangent to the direction of the electric field.
In this video we do a couple of examples about the calculation of the electric field.