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