Linear Accelerators (LINACs) technology is evolving towards compactness and high intensity. As a consequence, these devices are becoming suitable for several industrial and medical applications, such as the upgrade of light sources to the so-called 4-th generation or the design of high-dose rate radio-therapy facilities. In such scenarios, intensity-dependent collective effects can arise and compromise the LINAC performance. This work focuses on the Beam Loading effect, which induces a reduction of the available accelerating gradient of the structure as a consequence of the interaction of the beam with the cavity. This seminar covers an insight of the physical model derived in order to account for this effect, simulations and contrast with experimental measurements.