The concepts of derivative and integral are fundamental to understanding various fields related to qEEG, such as basic neuronal physiology, electromagnetism, or the Fourier transform. Therefore, it is necessary to begin by defining a function, which can be considered as the voltage of each of the EEG channels. The differential and derivatives are then discussed, including ordinary, successive, and partial derivatives. The inverse operation of the derivation is integration. Therefore, the concept of the Riemann integral will be briefly discussed which is sufficient for our purpose. Multiple integrals are essential in electromagnetism and will be briefly introduced. Due to their relevance, the properties of some special functions will be analyzed, such as trigonometric functions (sine, cosine, tangent, etc.) and exponential, logarithmic, or hyperbolic functions.