Gauge theory is a framework in theoretical physics that describes how fundamental forces operate through fields. It is based on the idea that certain symmetries in physical systems can lead to the existence of force-carrying particles, known as gauge bosons. This approach is essential for understanding the interactions of particles in the Standard Model of particle physics, which includes the electromagnetic, weak, and strong forces. In gauge theory, the concept of "gauge invariance" plays a crucial role, meaning that certain transformations do not change the physical outcomes of a system. This principle helps physicists formulate equations that accurately describe how particles interact, leading to predictions that can be tested through experiments, such as those conducted at the Large Hadron Collider.