Electric field: The electric field at a point is defined as the electrostatic force per unit test charge acting on a vanishingly small positive test charge placed at that point. Hence
The electric field is a vector quantity whose direction is same as that of the force F exerted on a positive test charge.
In SI unit is Newton per coulomb. It is equivalent to volt per meter.
Physical significance of electric field:
The force experienced by the test charge q0 is different at different points. So also varies from points to point.
By knowing electric field at any pint, we can determine the force on a charge placed at that point.
Electrostatic force = charge*electric field
Thus an electric field plays an intermediary role in the forces between two charges.
Charge ↔electric field ↔ charge