A state function is a property of a system that depends only on its current state, not on the path taken to reach that state. Common examples of state functions include temperature, pressure, volume, and enthalpy. These properties can be measured at any given moment and are used to describe the system's condition. In thermodynamics, state functions are crucial for understanding energy changes in processes. For instance, the change in internal energy of a system is a state function, meaning it only depends on the initial and final states, regardless of how the system transitioned between them.