The field lines really don't exist.
They are just geometric constructs made to study the electric field.
The lines point in the local direction of the electric field vector.
Since, the positive charge placed in external field experiences a force along the field, the field lines also give the direction of force a positive charge placed in that point experiences.
Properties of field lines would be,
1) Electric field lines begin at the positive charges and end at the negative charges. They may also diverge to infinity.
2) Two electric field lines would never cross each other since at the interse point, the electric field vector would have two directions which is absurd.
3) Field lines can never terminate midway. As stated earlier. They can begin and end at charges or can diverge to infinity. In case of a conductor present, the field lines meet the conductor's surface normally.