Electric field lines kinda confuse me!!!

Teacher told me that inside a conductor, the electric field is zero. But i wonder why?

And also if it is zero inside the conductor then why are there still electric field lines outside a conductor?

Preamble- I'v got little idea about physic but let me share something with you.

In moment of a force about a point, its formular is force applied multiplied by the perpendicular distance. Here a axis is chosen to which respect, the distance will b calculated. Its given that any force acting on the axis chosen will be zero.

Main point- In a conductor, a simple calculation enables the average drift speed of electrons to be estimated, knowing that conductors conduct as a result of electrons per unit volume and that each electron carries a charge é <electron flow>.

Knowing fully well that masses in earth's gravitational field have forces on them due to the earth's gravitational attraction. **In a similar way, the ELECTRIC FIELD In the space round a charge Q produces a force on a charge placed near Q**. The attraction is the Electric field... So the electron charges attracts too, but the force/pull on the charges outside the conductor is magnanimous compared to the negligible internal electron pull.

Reference: NELKON AND PARKER.