Gauge Field: A gauge field is a vector field that is used to describe the fundamental forces in gauge theories. It mediates the interactions between particles and determines the dynamics of the system.
Gauge Transformation: A gauge transformation is a change in the gauge field that leaves the physical observables unchanged. It represents the freedom to choose a different representation of the gauge field without affecting the underlying physics.
Gauge Invariance: Gauge invariance is the principle that the laws of physics must be independent of the choice of gauge, ensuring that the physical predictions of a theory are not affected by the specific representation of the gauge field.