Variable stars are celestial objects whose apparent brightness fluctuates over the span of time, making them invaluable tools for astrophysics. These changes in luminosity can result from various physical mechanisms, including radial pulsation of the stellar atmosphere, changes in the stellar radius, or complex interactions within multiple stellar components. Different types of variability exist, ranging from predictable, cyclical periods, such as those observed in pulsating giants, to erratic, sudden changes caused by accretion events or eruptive phenomena. By monitoring the brightness changes of these stars, scientists can determine crucial parameters like distance, size, and evolutionary stage for entire stellar populations, helping to map the structure and dynamics of galaxies and the universe.