The principle of superposition states that the net electric field at a point due to multiple charges is the vector sum of the individual fields from each charge. It applies to linear systems, meaning if a function is linear, the sum of the outputs for individual inputs equals the output for the sum of those inputs. This principle is crucial in electromagnetism and quantum mechanics, where the electric field behaves linearly with respect to charge distributions. Understanding this allows for the calculation of the electric field for combined charge distributions based on known fields from individual charges. The superposition principle is foundational in analyzing complex systems in physics.