The most fundamental idea behind electrostatics is that opposite charges attract and like charges repel. Also, charges that are separated by a distance have a force acting between them (either attractive or repulsive) proportional to the square of the distance separating them. (Twice as far away, 1 over 2 squared or 1/4th the force. Twice as close, 2 squared or 4 times the force.)
Charges will move if they can to equalize or neutralize the force between them.
More on electrostatics requires knowledge of the fundamental particles that have the property of charge. The electron is most prominent, and the proton is second to it.