The lines of force exert a lateral pressure on each other. What does this property of lines of force lead to explain?

Hint: The lines of force are parallel to each other in a uniform electric field, thus do not intersect with each other. The field lines originate from the positively charged body and terminate on the negatively charged particles.

Complete step by step solution:
The electric lines of forces are imaginary curved or straight lines that are drawn in an electric field. The direction of force at any point in these lines is given by drawing a tangent to that point. The lines of force have a tendency to contract lengthwise, thus two, unlike charges, attract each other.
But these lines have a tendency to expand laterally, so they exert lateral pressure on the nearby lines of force. This means that lines of force exert lateral pressure on each other, which makes them look like they repel each other. This explains why, when two similar charged objects are brought near each other they repel each other, this property of the lines of force is what causes the repulsion between them.
The electric lines of force are imaginary but they represent a real field, if a small positive charge, when not acted upon by some other force is kept in this field, it will travel along the length of these lines. A negative charge would travel in the opposite direction.

Note: For the electric field, the field lines can stretch up to infinity, they originate at a positive charge and terminate only at a negative charge. Thus the electric monopoles are possible, unlike the magnetic poles which do not exist, because the magnetic field lines form a closed loop.